I don't think we should change /dev/random. For a very long time, the notion is that the bits from /dev/random really are ok for keys, and there has been a notion that such bits are precious and you should be prepared to wait. If you aren't generating a key, you shouldn't read from /dev/random.
So I think rust is wrong and should be fixed. I can see the reason for frustration, but I believe that we should not break things that are sensible because they are abused and cause problems in some environments. It would also be reasonable to have a sysctl to allow /dev/random to return bytes anyway, like urandom would, and to turn this on for our xen builders, as a different workaround. That's easy, and it doesn't break the way things are supposed to be for people that don't ask for it. Also, on the xen build hosts, it would perhaps be good to turn on entropy collection from network and disk. Another approach, harder, is to create a xenrnd(4) pseudodevice and hypervisor call that gets bits from the host's /dev/random and injects them as if from a hardware rng.
