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Date: Mon, 31 Jan 2022 07:17:08 +0100
From: Salvatore Bonaccorso <carnil@...ian.org>
To: oss-security@...ts.openwall.com
Subject: Re: xterm buffer overflow via crafted sixel
Hi,
On Sun, Jan 30, 2022 at 12:27:38PM -0500, nick black wrote:
> howdy! in the hopes of further distributing my computing into
> your terminal emulators, i this morning learned that i can
> control writes to memory from XTerm's context via the method of
> crafted sixel. en garde, i'll let you try my wu-tang style.
>
> this was discovered while working on Notcurses bug #2573:
>
> https://github.com/dankamongmen/notcurses/issues/2573
>
> an error of mine own led to emission of a corrupted sixel [0], and
> spectacular gyrations from XTerm:
>
> ==1426124== Invalid write of size 2
> ==1426124== at 0x193FF1: set_sixel (graphics_sixel.c:181)
> ==1426124== by 0x1949E1: parse_sixel (graphics_sixel.c:534)
> ==1426124== by 0x17203D: do_dcs (misc.c:4973)
> ==1426124== by 0x149E03: doparsing.constprop.0 (charproc.c:4224)
> ==1426124== by 0x14B383: VTparse (charproc.c:5183)
> ==1426124== by 0x14B670: VTRun (charproc.c:8163)
> ==1426124== by 0x12DC49: main (main.c:2911)
> ==1426124== Address 0xffffffff0941efb8 is not stack'd, malloc'd or (recently) free'd
> ==1426124==
> ==1426124==
> ==1426124== Process terminating with default action of signal 11 (SIGSEGV): dumping core
> ==1426124== Access not within mapped region at address 0xFFFFFFFF0941EFB8
> ==1426124== at 0x193FF1: set_sixel (graphics_sixel.c:181)
> ==1426124== by 0x1949E1: parse_sixel (graphics_sixel.c:534)
> ==1426124== by 0x17203D: do_dcs (misc.c:4973)
> ==1426124== by 0x149E03: doparsing.constprop.0 (charproc.c:4224)
> ==1426124== by 0x14B383: VTparse (charproc.c:5183)
> ==1426124== by 0x14B670: VTRun (charproc.c:8163)
> ==1426124== by 0x12DC49: main (main.c:2911)
>
> I reported this to Mr. Thomas Dickey, the Archfather, and
> offered to put a patch together this evening. I also told him I
> probably wouldn't bother with a CVE, regarding which I clearly
> changed my mind pretty much immediately. Sorry, my good man =\.
>
> This requires that XTerm was built with Sixel support, and that
> the XTerm configuration interprets Sixels.
>
> --nick
>
> [0] "a man of genius makes no mistakes -- his errors are
> volitional, and the portals to discovery." (james joyce).
> nah, just kidding, i totally screwed it up.
This issue has CVE-2022-24130 assigned.
Regards,
Salvatore
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