Rustls doesn't really have to deal with the timing attack issue, because those issues are handled by the underlying crypto library, ring. And, ring wasn't built

Rustls doesn't really have to deal with the timing attack issue, because those issues are handled by the underlying crypto library, ring. And, ring wasn't built from scratch. It builds upon all the constant-time crypto code in BoringSSL and OpenSSL. And, we've improved the constant-timedness of the code in several ways and contributed most of those improvements back to BoringSSL.