Date: Thu, 11 Oct 2018 10:42:54 +0200 From: Emilio Pozuelo Monfort <pochu27@...il.com> To: oss-security@...ts.openwall.com, Hanno Böck <hanno@...eck.de>, Eddie Chapman <eddie@...k.net> Subject: Re: ghostscript: bypassing executeonly to escape -dSAFER sandbox (CVE-2018-17961) On 10/10/2018 17:04, Hanno Böck wrote: > On Wed, 10 Oct 2018 15:36:52 +0100 > Eddie Chapman <eddie@...k.net> wrote: > >> But I'm still unclear how "just browsing a website is enough to >> trigger the vulnerability in some common configurations." Are we >> talking about the user looking in their web browser cache directory >> on the filesystem using Nautilus, and hence running malicious code >> embedded in a cached file via the evince thumbnailer on opening that >> directory? Or maybe Nautilus/Gnome automatically runs the thumbnailer >> on every new file created in the user's home directory (via >> inotify?), including whatever the browser saves in the background >> (hopefully not)? Or is it just a case of the user opening a >> downloaded file with evince and becoming a victim that way? Though >> that is not exactly automatic, most browsers show a prompt asking >> what to do with a downloaded file. > > I don't know what exactly Tavis was referring to, but a scenario that > has been discussed in the past and likely is still possible in many > configurations is this: > Some browsers (notably chrome) will download files without asking in > their default configuration. So a site can make you download a file and > it ends up in your ~/Downloads dir. > > Desktop search tools will automatically index that (tracker from gnome, > baloo from kde). So voila - you can fire up an exploit if you can > exploit anything that tracker or baloo support. tracker-extract / miners run in a sandbox these days. No idea about baloo. https://bugzilla.gnome.org/show_bug.cgi?id=764786 Cheers, Emilio > https://scarybeastsecurity.blogspot.com/2016/11/0day-poc-risky-design-decisions-in.html > > Though I'm not sure if either of them uses ghostscript, a quick check > it seems that not. You still have the automatic download issue in > chrome, but you'd need to convince your user to open up ~/Downloads in > a file manager. That's a minor not-fully-automatic part, but I guess > it's plausible enough that users will eventually do that at some point. >
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