lkml.org 
[lkml]   [2002]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] (0/4) Entropy accounting fixes
On Sat, Aug 17, 2002 at 11:51:52PM -0400, Robert Love wrote:
> On Sat, 2002-08-17 at 23:05, Linus Torvalds wrote:
>
> > This is particularly true on things like embedded routers, where the
> > machine usually doesn't actually _run_ much user-level software, but is
> > just shuffling packets back and forth. Your logic seems to make it not add
> > any entropy from those packets, which can be _deadly_ if then the router
> > is also used for occasionally generating some random numbers for other
> > things.
>
> Agreed. Further, embedded routers - since they are headless/diskless -
> have problems even with the _current_ /dev/random code. They simply do
> not generate enough entropy to fulfill sshd requests [1].

This analysis actually stemmed from my work to port OpenSSH to a headless
(non-UNIX, non-POSIX, non-protected-memory, diskless) network appliance. SSH
only needs real entropy for the keys generated by ssh-keygen. It's
complete overkill for session keys.

And guess what? Stock Portable OpenSSH (v3.4p1) uses /dev/urandom
(configure.ac):

# Check for user-specified random device, otherwise check /dev/urandom
AC_ARG_WITH(random,
[ --with-random=FILE read entropy from FILE
(default=/dev/urandom)],

> Saying "use /dev/urandom" in this case means we may as well not have a
> /dev/random. There is a difference between incorrect accounting (which
> it seems you have identified) and just too strict gathering behavior.
>
> Robert Love
>
> [1] this is why I wrote my netdev-random patches. some machines just
> have to take the entropy from the network card... there is nothing
> else.

This patch is perfectly compatible with your netdev-random patches, in
fact I encourage it's resubmission after this one gets
in. /dev/urandom users will get all the benefits of network sampling
without /dev/random suffering at all.

--
"Love the dolphins," she advised him. "Write by W.A.S.T.E.."
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:28    [W:0.174 / U:0.424 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site