Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264895AbUFMIdX (ORCPT ); Sun, 13 Jun 2004 04:33:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265024AbUFMIdX (ORCPT ); Sun, 13 Jun 2004 04:33:23 -0400 Received: from sziami.cs.bme.hu ([152.66.242.225]:39297 "EHLO sziami.cs.bme.hu") by vger.kernel.org with ESMTP id S264895AbUFMIdV (ORCPT ); Sun, 13 Jun 2004 04:33:21 -0400 Date: Sun, 13 Jun 2004 10:33:08 +0200 (CEST) From: Koblinger Egmont X-X-Sender: egmont@sziami.cs.bme.hu To: Kalin KOZHUHAROV Cc: LKML Subject: Re: information leak in vga console scrollback buffer In-Reply-To: <40CBC094.6050901@ThinRope.net> Message-ID: References: <20040612204352.GA22347@taniwha.stupidest.org> <20040612205903.GA22428@taniwha.stupidest.org> <40CBC094.6050901@ThinRope.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1925 Lines: 50 On Sun, 13 Jun 2004, Kalin KOZHUHAROV wrote: > OK, I think I got what you are trying to point out. > To reproduce: > 1. login to a (vga) console. > 2. less /etc/services; press space t oscroll a few screens > 3. logout > 4. login again on the same console (possibly as a different user) > 5. less /etc/resolv.conf > 6. press UpArrow, then Shift+PgUp > > What is expected: > screen should not scroll past your file. > > What happens: > You can view the previous text (from /etc/services)!!! Here you didn't clear the scrollback buffer. Maybe you (or getty) executed a clear or a terminal reset but that only affects the visible part and not the scrollback buffer. There's absolutely no problem so far since everyone knows that the scrollback buffer only disappears when you switch to a different console. My problem is that with a really-not-trivial-command-and-key-combination you can possibly see /etc/services (in your example) even _after_ you've switched to a different console and you are certain that the scrollback buffer is no longer available. And then what if it's not /etc/services but some private data of yours? Maybe other users can later access it. There's no way you can protect yourself against it. And you live in a false belief that your private data is scrolled out forever. Please forget your own test case. Repeat _exactly_ those steps _I_ described in my original post. Then you'll understand what I'm talking about. You sure won't understand my problem if you believe that I'm wrong and want to convience me with your own interpretation of my words and your own (completely different) test case. Please stick to exactly what I reported. -- Egmont - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/