Date: Wed, 17 Oct 2018 02:14:46 -0400 From: Rich Felker <dalias@...c.org> To: oss-security@...ts.openwall.com Cc: Perry Metzger <perry@...rmont.com> Subject: Re: ghostscript: 1Policy operator gives access to .forceput CVE-2018-18284 On Tue, Oct 16, 2018 at 01:33:32PM -0700, Tavis Ormandy wrote: > On Tue, Oct 16, 2018 at 12:57 PM Perry E. Metzger <perry@...rmont.com> > wrote: > > > On Tue, 16 Oct 2018 11:06:14 -0700 Tavis Ormandy <taviso@...gle.com> > > wrote: > > > Side note: I'm done looking at ghostscript for now, but still > > > *strongly* recommend that we deprecate untrusted postscript and > > > disable ghostscript coders by default in policy.xml. > > > > Again, given that PostScript is an archival format for a lot of > > documents, wouldn't a version of ghostscript with all the ability to > > do anything dangerous removed from the interpreter at compile time be > > rational? > > > > > We have to work with what we've got. > > Even with the easy to exploit stuff compiled out (which upstream do not > support), I haven't been bothering to get CVE's for all the memory > corruption or UaF I've been reporting, because nobody can keep up with > these operator leaks anyway. An obvious fix for UaF's would be just removing the frees. Use of gs as an interactive program where leaks would matter is a historical curiosity; the only meaningful modern use is as a converter. If someone insists there are still uses where freeing matters, something like talloc may be a reasonable solution, removing all the internal frees and only performing frees of the whole context. Rich
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