Date: Wed, 10 Oct 2018 02:55:17 +0000 From: Doran Moppert <dmoppert@...hat.com> To: oss-security@...ts.openwall.com Cc: Bob Friesenhahn <bfriesen@...ple.dallas.tx.us> Subject: Re: ghostscript: bypassing executeonly to escape -dSAFER sandbox (CVE-2018-17961) Given the number of eyes & hours on these issues my question has to be naive, so I apologise, but couldn't seccomp provide a safe "safe mode" relatively easily? What syscalls does legit ghostscript need once the input and output streams are open? On Tue, Oct 09, 2018 at 06:34:23PM -0400, Alex Gaynor wrote: >Would they consider making a build-time "safe PS only" flag that ensured it >was compiled without things like shell-invocation? Then we could just try >to convince Linux distros to package it that way :-) > >Alex > >On Tue, Oct 9, 2018 at 6:33 PM Tavis Ormandy <taviso@...gle.com> wrote: > >> On Tue, Oct 9, 2018 at 3:27 PM Perry E. Metzger <perry@...rmont.com> >> wrote: >> >> > I keep wondering if there isn't a way to fully remove the dangerous >> > bits from a postscript interpreter so it can _only_ be used to view >> > the document and literally has no file system access compiled in at >> > all, so there's no way to touch the fs etc. regardless of what flags >> > the interpreter is invoked with. >> > >> > (I, too, find removing the ability to look at historical postscript >> > documents a bit more draconian than I like.) >> > >> > >> I've discussed it with upstream, it's a hard no because they feel it would >> make ghostscript non-conforming (i.e. non-conforming with the Adobe >> PostScript Language Reference Manual) >> >> We probably have similar thoughts on this, but that is the final word from >> upstream. >> >> Tavis. -- Doran Moppert Red Hat Product Security
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