Date: Sat, 20 Oct 2018 11:42:20 +0000 From: Jordan Glover <Golden_Miller83@...tonmail.ch> To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Subject: Re: Attempting to patch ghostscript-9.25 ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Saturday, October 20, 2018 3:47 AM, Ken Moffat <zarniwhoop@...world.com> wrote: > Hi, > > I hope people can read this - I know that google marks my mails as > spam (so no point Cc'ing Tavis) and also that Suse discard my mails. > Probably many other places also do that. Anyway: > > When the first set of vulnerabilities in 9.25 came out there was a > nice 'mostly harmless' example, and I patched BLFS for that (needed > one extra commit beyond the two Tavis specified, so that I could > make sense of where to apply part of it). > > For the later vulnerabilities, working out what to apply has been > much harder. Either everyone else thinks that other mitigations > against untrusted ps files will suffice, or else it's on everybody's > ToDo lists. > > So, here is a first attempt to fix all this month's vulnerabilities. > For the latest exploit(s) I do not have an example, so I don't know > whether or not this works. But it prevents the earlier > vulnerability, and usage of real ps (and eps - I only have the gs > examples, and only gs seems able to use them) seems to work > correctly. Unlike my first attempt to fix this, which turned out > to fail to display any ps, eps files. > > The patch is a bit big, so I've uploaded it to > http://www.linuxfromscratch.org/~ken/provisional/ as > ghostscript-9.25-security_fixes-2.patch > > 'provisional' until I find out if it protects adequately. If there > turn out ot be problems, I suppose I'll need to renumber later > versions. > > Built in BLFS using the same instructions as for the earlier -1 > patch [ http://www.linuxfromscratch.org/blfs/view/svn/pst/gs.html ] > but that doesn't mean it will work for everyone else's ways of > building. Note tht I do build the shared library. > > The patch lists which upstream commits I pulled in. I was mostly > concentrating on changes to gs_init which would maybe help me apply > the needed patches. As I've noted in the patch's introduction, > several commits had negative offsets (I guess hunks of code were > removed in some of the unrelated commits that I ignored). > > Comments welcome. > > One final thought - apart from 9.25, upstream seem to have an > approximately 6-monthly release schedule, so probably the only thing > likely to speed up 9.26 is everybody patching ;) > > ĸen I think the easiest way is to build on upstream git snapshot. All of its contents will be included in future release anyway. Jordan
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