Genuine question as I'm not a Rust professional, but if one was able to maintain the C API and headers to produce a drop in replacement for the current openssl implementation, would rewriting it in Rust produce a safer variant?
This would be based off using the #[no_mangle] extensively, I presume, probably with some amount of "unsafe" usage? At which point has the primary use case of Rust in this situation been lost?
What you're probably looking for is this project, which is a C API (I think ABI compatible) wrapper around Rustls that can be a "drop-in" replacement for OpenSSL: https://mesalink.io/
(note: not commenting on if one should or should not use it, only mentioning it's existence)
This would be based off using the #[no_mangle] extensively, I presume, probably with some amount of "unsafe" usage? At which point has the primary use case of Rust in this situation been lost?