Re: [uml-devel] [PATCH 3/9] UML - "Hardware" random number generator

From: Jeff Dike
Date: Fri Mar 11 2005 - 13:45:54 EST

rob@xxxxxxxxxxx said:
> I'm just thinking about those UML hosting farms, with several UML
> instances per machine, on machines which haven't got a keyboard
> attached constantly feeding entropy into the pool. If just ONE of
> them is serving ssl connections from its own /dev/urandom, that would
> drain the /dev/random entropy pool on the host machine almost
> immediately...

All true (except for that last reference to urandom), but also irrelevant to
whether UML's hwrng should be hooked up to the host's /dev/random or not.

As far as I can see, the only thing that matters is that hwrng should produce
real randomness, and that can only be had by reading /dev/random (or maybe
the host's /dev/hwrng, but that's supposed to be fed into /dev/random anyway).

So, hooking up the UML /dev/hwrng to the host's /dev/urandom would be lying.

If the host's entropy pool gets drained as a result, I would say that's an
application bug, and not a reason for UML to get its randomness from the
host's /dev/urandom.


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