linux-kernel - Re: drivers/char/random.c: more ruminations

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Message-ID: <20140610012036.GA8092@thunk.org>
Date:	Mon, 9 Jun 2014 21:20:36 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	George Spelvin <linux@...izon.com>
Cc:	hpa@...ux.intel.com, linux-kernel@...r.kernel.org,
	mingo@...nel.org, price@....edu
Subject: Re: drivers/char/random.c: more ruminations

On Mon, Jun 09, 2014 at 08:20:57PM -0400, George Spelvin wrote:
> 
> I have an idea for a patch to change _xfer_secondary_pool
> to use extract_buf rather than extract_entropy; is all that
> FIPS stuff needed for purely internal transfers?

That's not the part of extract_entropy() which is critical.  What's
critical is the control over only transfering entropy when there is at
least a certain minimum amount of entropy.  This provides the
Yarrow-like avalanche property which is required to provide recovery
after the internal state of the entropy pools have been exposed.

> Also, shouldn't the r->last_pulled holdoff in xfer_secondary_pool be
> really limited to actual transfers?  I.e. reorder the conditions as...

Yes, that makes sense.

Cheers,

						- Ted
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