Messages in this thread |  | | | Date | Thu, 24 Mar 2011 15:15:53 +0100 | | From | Petr Pisar <> | | Subject | Re: [PATCH] Clean console safely |
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On Thu, Mar 24, 2011 at 10:24:31AM +0000, Alan Cox wrote: > On Thu, 24 Mar 2011 10:56:51 +0100 > Petr Písař <ppisar@redhat.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. > The problem with DECSRC as well as DECSTR or RIS is they reset terminal font, keyboard layout, unicode mode and other configuration. That's the reason why I rejected enhancing RIS implemented in Linux VT already. In other words, I'm searching for a clear display feature which preserves configuration. I read console_codes(4), console_ioctl(4), and now the VT520 documentation and I did not find any existing control code. The most close seems ED J for me.
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