On Fri, Sep 19, 2014 at 11:30 AM, Christopher Covington
[off-list ref] wrote:

On 09/17/2014 10:50 PM, Andy Lutomirski wrote:

quoted

Hi all-

I would like to standardize on a very simple protocol by which a guest
OS can obtain an RNG seed early in boot.

The main design requirements are:

 - The interface should be very easy to use.  Linux, at least, will
want to use it extremely early in boot as part of kernel ASLR.  This
means that PCI and ACPI will not work.

How do non-virtual systems get entropy this early? RDRAND/Padlock? Truerand?
Could hypervisors and simulators simply make sure these work?

If RDRAND is available, then Linux, at least, will use it.  The rest
are too complicated for early use.  Linux on x86 plays some vaguely
clever games with rdtsc and poking at the i8254 port.

I think that these tricks are even less useful as a guest than they
are on metal, and we can use paravirt mechanisms to make guest early
boot rngs much stronger.

--Andy