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Date:      Wed, 24 Apr 2002 02:37:23 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Robert Watson <rwatson@FreeBSD.ORG>
Cc:        Greg 'groggy' Lehey <grog@FreeBSD.ORG>, Jordan Hubbard <jkh@winston.freebsd.org>, Oscar Bonilla <obonilla@galileo.edu>, Anthony Schneider <aschneid@mail.slc.edu>, Mike Meyer <mwm-dated-1019955884.8b118e@mired.org>, hackers@FreeBSD.ORG
Subject:   Re: Security through obscurity? (was: ssh + compiled-in SKEY support  considered harmful?)
Message-ID:  <3CC67CD3.A16A0F66@mindspring.com>
References:  <Pine.NEB.3.96L.1020423205451.55944H-100000@fledge.watson.org>

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Robert Watson wrote:
> On Wed, 24 Apr 2002, Greg 'groggy' Lehey wrote:
> > > A more conservative default configuration results in a material
> > > improvement in system security.
> >
> > *snip*
> 
> By snipping here, you removed reference to the fact that this was a
> general discussion of direction and policy, rather than specifically to do
> with X11, which provides an answer to a number of your questions.

People really try to avoid policy decisions; they trap them
into doing in the future what they say now that they will do
in the future (damned consistency!).


> As indicated, not all of these criteria may apply in every case -- this
> was just a suggested list of criteria that might be applied.  There have
> been a number of vulnerabilities in a number of different X protocol
> implementations.  Many of them require first getting past the normal X
> access control mechanisms before they may be exploited, but not all.

???

Which ones don't require that?  The only ones I can think of are
TCP vulnerabilities (as I said before), and you aren't going to
fix a TCP vulnerability unless you turn off *all* TCP-based services,
not just X11.


> If you think that's a problem, then you didn't read my e-mail.  However,
> there is actually a great deal of relevance here: protocol and
> implementation complexity have a lot to do with the chances that there
> will be a serious vulnerability.  Likewise, the level of privilege
> associated with X11 is highly relevant: if you compromise the X server,
> you've got a lot to play with.

I keep hearing "complexity := vulnerability".  I'd really, really
like to see a mathematical proof of this theory.

[ ... ]

> We adapt a number of applications for the FreeBSD environment and
> configuration.  A more common way to distinguish our localizations is
> through a WITH_GRATUITOUS_LOCAL_CHANGES make argument, or via an
> interactice interface (for example, ghostscript).

8-) 8-) I like it.


[ ... ]

> If we can expose this feature via
> rc.conf, just make it a seperate rc.conf entry and twiddle it off of the
> security configuration manu in sysinstall.  Is that something we can do
> easily?

I think the way to do this is with firewall rules.  Making everything
read rc.conf is a pretty useless thing to do.  It's also dangerous to
make a single rc.conf line apply to more than one thing, since then it
permits alternate (potentially conflicting) interpretations of meaning.

-- Terry

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