It's important to note here that Linux's behaviour is broken, plain and simple: /dev/random blocks even if properly seeded, and /dev/urandom doesn't block even

It's important to note here that Linux's behaviour is broken, plain and simple: /dev/random blocks even if properly seeded, and /dev/urandom doesn't block even if improperly seeded. The Real Solution™ is to make /dev/random and /dev/urandom the same thing, and make them both block until properly seeded. And replace the current ad-hoc CSPRNG with a decent one, e.g. Fortuna. There were patches almost 15 years ago implementing this (https://lwn.net/Articles/103653/ https://lwn.net/Articles/103653/), but they were rejected. There's simply no good reason not to fix Linux's CSPRNG.