Add article on evil-nix

2023-06-28-evil-nix.md

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+title: evil-nix: download files without requiring a hash
+summary: A Nix library that allows downloading files without requiring a hash, even in pure-eval mode
+tags: nixos
+draft: false
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+
+I recently released a Nix library called
+[`evil-nix`](https://github.com/cdepillabout/evil-nix).  It allows downloading
+files without requiring a hash on the file.  It even works in Nix's
+[`pure-eval`](https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-pure-eval)
+mode.
+
+`evil-nix` exploits Nix support for unsafe hash functions (like SHA1) in
+fixed-output derivations. It uses SHA1 hash collisions to sneak data from the
+internet out of fixed-output derivations.
+
+Due to the implementation, `evil-nix` is extremely inefficient with downloading
+files. I don't recommend the library to actually be used in practice, but it is
+a neat trick.
+
+Take a look at the [README.md](https://github.com/cdepillabout/evil-nix#readme)
+for more information.