linux-kernel - Re: [PATCH] Clean console safely

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Date:	Thu, 24 Mar 2011 10:24:31 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Petr Písař <ppisar@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Clean console safely

On Thu, 24 Mar 2011 10:56:51 +0100
Petr Písař <ppisar@...hat.com> wrote:

> Traditional \E[2J sequence erases console display but scroll-back
> buffer and underlying device (frame) buffer keep data that can be
> accessed by scrolling console back.
> 
> This patch introduce new \E[J parameter 3 that allows to scramble
> scroll-back buffer explicitly. Session locking programs (screen,
> vlock) can use it to prevent attacker to browse locked console
> history.
> ---
>  drivers/tty/vt/vt.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)

Looks sensible enough

There are a set of official codes that are probably more relevant, and
also deal with the timing of events

See DECSR/DECSRC on a later VT terminal, also DECSTR which 

DECSR = secure reset, return to power up state, \E[n+p where n is an
optional value from 1-16383 which if provided is replied back from the tty
as a DECSRC response (hence 'secure'). It's defined to clear off
screen memory, and also other weirdness a user may have set up so could
reasonably also be extended a bit if there is other stuff founbd in
future that such a reset really ought to clean up - eg for mingetty.

http://www.vt100.net/docs/vt520-rm/ek-vt520-rm.pdf (page 299)

ED 3J looks fine but is a new "made up" extension.

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