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Date: Mon, 31 Jan 2022 11:48:15 +0100
From: Jakub Wilk <jwilk@...lk.net>
To: <oss-security@...ts.openwall.com>
Subject: Re: Re: xterm buffer overflow via crafted sixel
* Tavis Ormandy <taviso@...il.com>, 2022-01-30, 18:39:
>I can repro here, here is a testcase:
>
>#!/bin/bash
>printf "\ePq"
>printf "#%hhu;2;%hhu;%hhu;%hhu" 0x41 100 100 100
>printf "#%hhu!%u@" 0x41 0x7fffffff
>printf "#%hhu!%u@" 0x41 0x7fffffff
>printf "\e\\"
>
>That should wrap context->col, and write a 'A' to graphic->pixels oob in
>set_sixel.
>
>I use `XTerm*decTerminalID: vt382` in .Xresources, not sure if that matters.
I think it does.
https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Sixel-Graphics
says "xterm [needs to be] configured as VT240, VT241, VT330, VT340 or
VT382" for Sixels to be supported. And indeed, I can't reproduce the bug
with the default emulation level (VT420).
If you don't want to tinker with your .Xresources for testing, you can
use the -ti option instead.
--
Jakub Wilk
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