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. knorker · 1790949498 · focus · HN ↗

         Supposed to be or not, it is.

         Package managers even use it. E.g. you can have a cargo dependency pointing to GitHub at a specific commit. It's definitely intended to provide end to end security without depending on GitHub being secure.

         Also git submodules.

         1. knorker · 1790966062 · focus · HN ↗

            And I should add: not just github compromise, but supply chain / original author replacing the contents.

            Absolutely the SHA-1 is treated as "authenticating". Cargo.lock (for regular crates.io dependencies) are confirmed using SHA-256.

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