Re: [ptxdist] [PATCH] haveged: add entropy daemon

[Alexander Dahl <post@lespocky.de>]

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Hello,

On Fri, Jun 30, 2017 at 02:16:07PM +0200, Michael Olbrich wrote:
> On Fri, Jun 30, 2017 at 09:19:18AM +0200, Alexander Dahl wrote:
> > Besides: is there any way to have this random generator stuff
> > certainly ready before generating dropbear keys (rc-once)?
> 
> I think /dev/random and getrandom() can block until then. Something could
> be built on top of that. However you need to be careful: This may block a
> very long time on an idle embedded system.

I had a look into dropbearkey now. As far as I understand the code,
dropbear just uses /dev/urandom, but tries to feed some entropy into
it before doing anything with randomness. The "documentation" in
default_options.h suggests /dev/random is used for keygen, but I think
it's wrong (our outdated) and only non blocking randomness is used.

dropbear can use prngd or egd, but no hint in the code on haveged. The
only thing I found on dropbear profiting from haveged is an old ticket
in the OpenWRT bugtracker, but they just do the "hopefully wait long
enough" thing. [1]

So I guess to improve this situation someone may have to talk to
upstream dropbear to discuss some possibilies?

Greets
Alex

[1] https://dev.openwrt.org/ticket/9631

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