lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 26 May 2008 23:11:21 +0100
From:	Ben Hutchings <>
To:	Bill Fink <>
Cc:	Krzysztof Halasa <>,
	Alejandro Riveira Fernández 
	<>, Theodore Tso <tytso@....EDU>,
	Glen Turner <>,
	Chris Peterson <>,
	Alan Cox <>,
	Lennart Sorensen <>,
	Jeff Garzik <>,
	"Kok, Auke" <>,
	Rick Jones <>,
	"Brandeburg, Jesse" <>,,
Subject: Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE_RANDOM

Bill Fink wrote:
> On Mon, 26 May 2008, Krzysztof Halasa wrote:
> > Bill Fink <> writes:
> > 
> > > Another idea that occured to me:  How about using the low order bits
> > > of the instruction memory address being executed that was interrupted
> > > by the HZ timer interrupt.
> > 
> > Think of constant-instructions-length processors :-)
> I'm not sure what you're driving at, but if it's that you shouldn't
> use the very last 2 or 3 bits, then sure those should be excluded.
> But that still leaves 9 or 10 bits at least in the page offset, and
> that's being conservative in the number of address bits to sample.

We would still need to exclude any tight loops which an attacker could
predict or influence a process to enter - the idle loop obviously, plus
udelay(), memcpy() and probably many other functions.  Some such loops may
be in userland and therefore unknown to us.  So there might not be nearly
as many bits of entropy in the program counter as could be naively
expected.  What's more, once userland is blocked on /dev/random, there is
no more entropy available from the program counter!


Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists