From: Matt Mackall <mpm@selenic.com>
To: Theodore Tso <tytso@mit.edu>, Kyle Moffett <mrmacman_g4@mac.com>,
Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, davem@davemloft.net
Subject: Re: [PATCH 7/14] random: Remove SA_SAMPLE_RANDOM from network drivers
Date: Fri, 5 May 2006 15:34:37 -0500 [thread overview]
Message-ID: <20060505203436.GW15445@waste.org> (raw)
In-Reply-To: <20060505191127.GA16076@thunk.org>
On Fri, May 05, 2006 at 03:11:27PM -0400, Theodore Tso wrote:
> On Fri, May 05, 2006 at 12:24:26PM -0500, Matt Mackall wrote:
> > I haven't seen such an analysis, scholarly or otherwise and my bias
> > here is to lean towards the paranoid.
> >
> > Assuming a machine with no TSC and an otherwise quiescent ethernet
> > (hackers burning the midnight oil), I think most of the
> > hard-to-analyze bits above get pretty transparent.
>
> As always, whether or not the packet arrival times could be guessable
> and/or controlled by an attacker really depends on your threat model.
> For someone who has an ethernet monitor attached directly to the
> segment right next to your computer, it's very likely that they would
> be successful in guessing the inputs into the entropy pool. However,
> an attacker with physical access to your machine could probably do all
> sorts of other things, such as install a keyboard sniffer, etc.
>
> For a remote attacker, life gets much more difficult. Each switch,
> router, and bridge effectively has a queue into which packets must
> flow through, and that is _not_ known to a remote attacker. This is
> especially true today, when most people don't even use repeaters, but
> rather switches/bridges, which effectly make each ethernet connection
> to each host its own separate collision domain (indeed that term
> doesn't even apply for modern high-speed ethernets).
>
> I've always thought the right answer is that whether or not network
> packet arrival times should be used as entropy input should be
> configurable, since depending on the environment, it might or might
> not be safe, and for some hosts (particularly diskless servers), the
> network might be the only source of entropy available to them.
Nonetheless, the current SA_SAMPLE_RANDOM scheme should go. A) it's in
the IRQ fast path B) most of its users are bogus which strongly
indicates it's a bad API.
Instead (if we want network entropy) we should add an
add_network_randomness call in some central location in the network
stack (probably right next to netpoll's RX hooks) and probably have it
compiled out by default.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2006-05-05 20:39 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-05 16:42 [PATCH 1/14] random: Remove SA_SAMPLE_RANDOM from floppy driver Matt Mackall
2006-05-05 16:42 ` [PATCH 6/14] random: Remove redundant SA_SAMPLE_RANDOM from touchscreen drivers Matt Mackall
2006-05-05 16:42 ` [PATCH 4/14] random: Change cpqarray to use add_disk_randomness Matt Mackall
2006-05-05 16:42 ` [PATCH 2/14] random: Remove redundant SA_SAMPLE_RANDOM from NinjaSCSI Matt Mackall
2006-05-05 16:42 ` [PATCH 3/14] random: Make CCISS use add_disk_randomness Matt Mackall
2006-05-05 16:42 ` [PATCH 5/14] random: Remove bogus SA_SAMPLE_RANDOM from at91 compact flash driver Matt Mackall
2006-05-05 16:42 ` [PATCH 8/14] random: Remove SA_SAMPLE_RANDOM from USB gadget drivers Matt Mackall
2006-05-06 11:07 ` Denis Vlasenko
2006-05-06 18:16 ` David Brownell
2006-05-06 18:31 ` Matt Mackall
2006-05-05 16:42 ` [PATCH 7/14] random: Remove SA_SAMPLE_RANDOM from network drivers Matt Mackall
2006-05-05 17:13 ` Kyle Moffett
2006-05-05 17:24 ` Matt Mackall
2006-05-05 19:11 ` Theodore Tso
2006-05-05 20:30 ` Stephen Hemminger
2006-05-05 20:34 ` Matt Mackall [this message]
2006-05-06 11:55 ` Theodore Tso
2006-05-06 16:48 ` Matt Mackall
2006-05-06 17:29 ` Bernd Eckenfels
2006-05-06 18:05 ` Theodore Tso
2006-05-06 20:33 ` Matt Mackall
2006-05-07 0:17 ` David S. Miller
2006-05-07 1:22 ` Theodore Tso
2006-05-07 5:07 ` Matt Mackall
2006-05-08 21:58 ` Sami Farin
2006-05-24 22:47 ` Marcin Dalecki
2006-05-25 0:08 ` Theodore Tso
2006-05-31 19:29 ` Bill Davidsen
2006-05-07 0:08 ` David S. Miller
2006-05-07 4:59 ` Matt Mackall
2006-05-07 5:46 ` David S. Miller
2006-05-07 16:31 ` Matt Mackall
2006-05-07 13:13 ` Thiago Galesi
2006-05-07 16:00 ` Matt Mackall
2006-05-07 17:00 ` Thiago Galesi
2006-05-08 0:13 ` Theodore Tso
2006-05-08 2:55 ` Matt Mackall
2006-05-08 6:26 ` Pavel Machek
2006-05-08 7:07 ` David S. Miller
2006-05-08 14:05 ` Matt Mackall
2006-05-08 17:21 ` Pavel Machek
2006-05-08 17:27 ` Matt Mackall
2006-05-09 11:23 ` Pavel Machek
2006-05-11 10:05 ` Ph. Marek
2006-05-24 22:35 ` Marcin Dalecki
2006-05-05 21:10 ` David S. Miller
2006-05-05 23:03 ` Matt Mackall
2006-05-05 23:19 ` David S. Miller
2006-05-06 14:08 ` Folkert van Heusden
2006-05-06 15:19 ` Lee Revell
2006-05-07 10:35 ` Folkert van Heusden
2006-05-07 16:33 ` Matt Mackall
2006-05-05 16:42 ` [PATCH 9/14] random: Remove SA_SAMPLE_RANDOM from i2c drivers Matt Mackall
2006-05-05 16:42 ` [PATCH 10/14] random: Remove bogus SA_SAMPLE_RANDOM from mpc52xx serial driver Matt Mackall
2006-05-05 16:42 ` [PATCH 11/14] random: Remove UML usage of SA_SAMPLE_RANDOM Matt Mackall
2006-05-05 16:42 ` [PATCH 13/14] random: Remove SA_SAMPLE_RANDOM from IRQ fastpath Matt Mackall
2006-05-05 16:42 ` [PATCH 12/14] random: Remove not very useful SA_SAMPLE_RANDOM from lubbock Matt Mackall
2006-05-05 16:42 ` [PATCH 14/14] random: Remove add_interrupt_randomness Matt Mackall
2006-05-08 7:38 [PATCH 7/14] random: Remove SA_SAMPLE_RANDOM from network drivers linux
2006-05-12 6:09 ` linux
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