OpenSSH (portable) and entropy gathering

[Dave Dykstra]

On Fri, Sep 28, 2001 at 10:13:50AM -0400, Dan Astoorian wrote:
> On Thu, 27 Sep 2001 20:41:05 EDT, Damien Miller writes:
> > On Thu, 27 Sep 2001, Dan Astoorian wrote:
> > 
> > > 
> > > It would (IMHO) be useful if there were a way to optionally configure
> > > that code to fall back to the internal entropy gathering routines in the
> > > event that EGD was not available; as it is, the routines simply fail if
> > > EGD is unavailable at the time the ssh daemon or client is invoked.
> > > 
> > > Is this a feature the OpenSSH Portability Team would consider
> > > worthwhile?
> > 
> > Probably not - in fact we want to deprecate the built in entropy 
> > collection in favor of the use of a daemon or subprocess.
> 
> I can understand that desire, and I don't mean to be argumentative, but
> I'm looking at it from the standpoint of a sysadmin.  Right now, my
> systems use the internal entropy gathering.  I _want_ to move to PRNGD.
> However, I don't want my systems to stop working entirely if PRNGD isn't
> running or if its socket gets clobbered.  For instance, I need the
> ability to run ssh *clients* from the console in single-user mode,
> before PRNGD has started up.
> 
> By not having an option to fall back, it's making it more difficult to
> justify the case for installing PRNGD, because functionality takes
> precedence over efficiency.
> 
> I don't see a downside to having a configure-time option (off by
> default) like "--with-entropy-fallback" to use the built-in code if (and
> only if) the daemon were unreachable, unless the OpenSSH Portability
> Team considers it better to fail completely than to use the deprecated
> code.
> 
> Am I missing something?
> 
> I'd be willing to code the change.


I submitted a patch to allow all sources of entropy to be selected at 
runtime.  Thread begins at
    http://marc.theaimsgroup.com/?l=openssh-unix-dev&m=99193668118573&w=2

It works by allowing you to specify multiple sources of entropy at
configure time, and choosing between them all at runtime.

I haven't updated it to 2.9.9p2 yet, I'll post it again when I do.
The last response from Ben was that it probably wouldn't get in until
after 3.0.

- Dave Dykstra