> the kind of app where you want to carefully audit the code line by line
This should be much less necessary for Safe Rust. The existing C sudo needs libpcre2, and OpenSSL neither of which are small - among other dependencies.
Some of these dependencies do use unsafe Rust in places, and so it's valuable that those places should be inspected carefully (and not only for sudo) - but many do not, humantime for example is entirely safe Rust. Is it possible it has a logic error of some sort? Yes. Is it likely it somehow introduces a security hole? Not really. A C equivalent could easily introduce a critical buffer overflow, use after free or similar but that's not possible in safe Rust.
sudo doesn't strictly need OpenSSL. That dependency is part of it's log server client implementation, and it's also available for the plugin system.
I had no idea sudo even had the need for plugins.
Which raises the question, maybe there's a need for two different sudo implementations. One that provides the simplest possible implementation of the feature, and another one that provides fancy log server and plugin integrations.
For something like this, I think I would actually prefer that they copied existing code for hashing. It's simple and stable enough to avoid taking a dependency.