Date: Tue, 7 Oct 2014 14:50:08 +0200 From: Sven Kieske <s.kieske@...twald.de> To: <oss-security@...ts.openwall.com> CC: <langsec-discuss@...l.langsec.org> Subject: Re: Thoughts on Shellshock and beyond On 07/10/14 13:59, David A. Wheeler wrote: > I am still struggling with this one. I am trying to create that list here: > http://www.dwheeler.com/essays/shellshock.html#detect-or-prevent > > But to be honest, that list is pretty pathetic. This is a challenging class of vulnerability to detect or prevent ahead of time. Ideas would be very welcome. Well I think the core issue was: A parser, which was written to just run trusted input was exposed years later via third party configuration ( e.g. /bin/sh == bash & cgi using /bin/sh) to untrusted input. I guess to avoid such cases in the future, you must be explicit from which sources you accept input. This whitelist should not contain arbitrary content like "stdin" or any input source which itself has no strict whitelist on input it accepts. So in short: you need to design and implement interfaces for every program which enforce explicit security boundaries. Example: why should I be able to feed audio files into graphics processing programs? This is a lot about parser and language safety imho. So I can't mention langsec.org enough. Go there, read the papers, look up the videos from their talks. I know this means re-implementing almost all code out there. But if you can proof that the input for program A constructs a turing complete grammar you have already lost. You can not "fix" these bugs, as there is an infinite number of them. You need to fix the parsers and the languages first. -- Mit freundlichen Grüßen / Regards Sven Kieske Systemadministrator Mittwald CM Service GmbH & Co. KG Königsberger Straße 6 32339 Espelkamp T: +49-5772-293-100 F: +49-5772-293-333 https://www.mittwald.de Geschäftsführer: Robert Meyer St.Nr.: 331/5721/1033, USt-IdNr.: DE814773217, HRA 6640, AG Bad Oeynhausen Komplementärin: Robert Meyer Verwaltungs GmbH, HRB 13260, AG Bad Oeynhausen
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