[Xen-devel] entropy for VMs

[Dave Scott <Dave.Scott@xxxxxxxxxx>]

Hi,

Mirage now has nice features like TLS[1] and therefore needs a good source of 
randomness to generate session keys. Mirage VMs are PV, so we canât use 
virtio-rng. We've created a prototype entropy server which may be of interest 
to other people too:

https://github.com/mirage/xentropyd

This behaves a bit like xenconsoled: it watches for domains being created and 
then connects to them via the console protocol. There is a little handshake[2] 
(to catch accidental screwups with the wrong console) and then the daemon feeds 
random data into the console through a rate-limiter. Mirageâs entropy driver 
can read the data from the console fairly easily[3]. I assume we could write a 
similar thing for linux too.

What do you think? (And does anyone know a better way (TM)?)

The code is still a bit of a prototype, and contains slightly forked versions 
of core Mirage libraries-- I need to sort that out before a 1.0.

Cheers,
Dave

[1] http://openmirage.org/blog/introducing-ocaml-tls
[2] https://github.com/mirage/xentropyd/blob/master/doc/protocol.md
[3] 
https://github.com/djs55/mirage-entropy/blob/981b070d78ae407015b1e8dedb3141b05454366f/xen/entropy_xen.ml#L130
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