Re: Re: CVE Request: libX11: buffer overflow in MakeBigReq macro

[Yann Droneaud <ydroneaud () opteya com>]

Hi,

Le jeudi 09 avril 2015 à 07:44 -0400, Marc Deslauriers a écrit :
> On 2015-04-09 07:10 AM, Florian Weimer wrote:
> > On 04/09/2015 09:09 AM, cve-assign () mitre org wrote:
> > > > The MakeBigReq macro in libX11 contained a 4-byte buffer overflow:
> > >
> > > > https://bugs.freedesktop.org/show_bug.cgi?id=56508
> > >
> > > > Fixed by the following commit in libX11 1.5.99.901:
> > >
> > > > http://cgit.freedesktop.org/xorg/lib/libX11/commit/?id=39547d600a13713e15429f49768e54c3173c828d
> > >
> > > (for the "#ifdef LONG64")
> > > > - memmove(((char *)req) + 8, ((char *)req) + 4, _BRlen << 2); \
> > > > + memmove(((char *)req) + 8, ((char *)req) + 4, (_BRlen - 1) << 2); \
> > >
> > > (for the "else")
> > > > - memmove(((char *)req) + 8, ((char *)req) + 4, _BRlen << 2); \
> > > > + memmove(((char *)req) + 8, ((char *)req) + 4, (_BRlen - 1) << 2); \
> > >
> > > Use CVE-2013-7439.
> >
> > Does this assignment cover application code which has to be recompiled
> > because it included an expansion of broken macro?
> >
> > (The question is hypothetical.  I could find copies of the header file,
> > but not actual users of the macro.)
>
> Actually, libx11 contains the following macro also:
>
> #define SetReqLen(req,n,badlen) \
>     if ((req->length + n) > (unsigned)65535) { \
>       if (dpy->bigreq_size) { \
>           MakeBigReq(req,n) \
>       } else { \
>           n = badlen; \
>           req->length += n; \
>       } \
>     } else \
>       req->length += n
>
> which means anything that uses SetReqLen also needs to be rebuilt, and so far
> I've found:
>
> libxext
> libxrender
> libxi
> libxfixes
> libxrandr
> libsdl1.2
> libxv
> libxp
> texlive-bin
> xserver-xorg-video-vmware

There's more candidates for SetReqLen:

http://codesearch.debian.net/results/SetReqLen/page_0

I've noted in particular cairo.

And then indirectly through a embedded copy of cairo:
firefox (iceweasel), thunderbird (icedove), texlive-bin, indigo,
wine-gecko.

Additionally vnc4 through its own libX11 copy.

Finally open-vm-tools is also a possible candidate.

(Please note I haven't check if the SetReqLen macro is actually used in 
a way that might trigger a buffer overflow in MakeBigReq macro).

Regards.

-- 
Yann Droneaud
OPTEYA