linux-kernel - Re: [PATCH v4 0/5] /dev/random

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Message-ID: <6920965.KzCBF1o6NP@positron.chronox.de>
Date:	Tue, 21 Jun 2016 20:05:01 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	"Austin S. Hemmelgarn" <ahferroin7@...il.com>
Cc:	Tomas Mraz <tmraz@...hat.com>, Theodore Ts'o <tytso@....edu>,
	David Jaša <djasa@...hat.com>,
	Andi Kleen <andi@...stfloor.org>, sandyinchina@...il.com,
	Jason Cooper <cryptography@...edaemon.net>,
	John Denker <jsd@...n.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Joe Perches <joe@...ches.com>, Pavel Machek <pavel@....cz>,
	George Spelvin <linux@...izon.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/5] /dev/random - a new approach

Am Dienstag, 21. Juni 2016, 13:54:13 schrieb Austin S. Hemmelgarn:

Hi Austin,

> On 2016-06-21 13:23, Stephan Mueller wrote:
> > Am Dienstag, 21. Juni 2016, 13:18:33 schrieb Austin S. Hemmelgarn:
> > 
> > Hi Austin,
> > 
> >>> You have to trust the host for anything, not just for the entropy in
> >>> timings. This is completely invalid argument unless you can present a
> >>> method that one guest can manipulate timings in other guest in such a
> >>> way that _removes_ the inherent entropy from the host.
> >> 
> >> When dealing with almost any type 2 hypervisor, it is fully possible for
> >> a user other than the one running the hypervisor to manipulate
> >> scheduling such that entropy is reduced.  This does not imply that the
> > 
> > Please re-read the document: Jitter RNG does not rest on scheduling.
> 
> If you are running inside a VM, your interrupt timings depend on the

The RNG does not rest on interrupts either.

> hpyervisor's scheduling, period.  You may not directly rely on
> scheduling from the OS you are running on, but if you are doing anything
> timing related in a VM, you are at the mercy of the scheduling used by
> the hypervisor and whatever host OS that may be running on.
> 
> In the attack I"m describing, the malicious user is not manipulating the
> guest OS's scheduling, they are manipulating the host system's scheduling.


Ciao
Stephan