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Date: Sat, 27 Sep 2014 16:09:51 -0400
From: Chet Ramey <chet.ramey@...e.edu>
To: Michal Zalewski <lcamtuf@...edump.cx>
CC: chet.ramey@...e.edu, Tavis Ormandy <taviso@...xchg8b.com>,
Florian Weimer <fw@...eb.enyo.de>, Solar Designer <solar@...nwall.com>,
oss-security@...ts.openwall.com
Subject: Re: CVE-2014-6271: remote code execution through bash
On 9/27/14, 3:39 PM, Michal Zalewski wrote:
>> STD::what::does::this::do
>
> We ran into this problem with the original patch at Google, but TBH,
> we've just bitten the bullet.
>
> I'm not sure how hard we should try to accommodate outliers like this
> specifically for functions - as far as I can tell, you can't really
> get away with meaningfully using colons in variable names, right? But
> if you just want to minimize breakage without getting into existential
> discussions, wouldn't wihtelisting : and perhaps periods and - going
> out on a limb - brackets be good enough?
We already make function names and variable names different, so there's
no going back -- variable names have the usual restrictions, but with
function names it's essentially anything goes.
Since we would be going from essentially anything goes to a very small
set of acceptable exceptions, I can see a steady stream of "I used to
be able to use character X in my function names and can't now." Frankly,
the really dangerous one is `/', since it allows you to circumvent scripts
that attempt to use full pathnames to bypass shell function lookups. I
am more interested in other dangerous characters, the existential debate
between whitelists and blacklists notwithstanding.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU chet@...e.edu http://cnswww.cns.cwru.edu/~chet/
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