linux-kernel - Re: [PATCH] Audit: Add TTY input auditing

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Date:	Thu, 7 Jun 2007 22:59:45 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Miloslav Trmac <mitr@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, dwmw2@...radead.org,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...hat.com>,
	Steve Grubb <sgrubb@...hat.com>,
	Alexander Viro <aviro@...hat.com>
Subject: Re: [PATCH] Audit: Add TTY input auditing

On Thu, 07 Jun 2007 16:20:07 +0200
Miloslav Trmac <mitr@...hat.com> wrote:

> Alan Cox napsal(a):
> >>> +			if (filp->f_op->read == tty_read) {
> >>> +				disable = 0;
> >>> +				break;
> > Why says a tty will always have f->op->read == tty_read ?
> AFAICS from tty_io.c, it will always be tty_read or hung_up_tty_read.
> Normal user processes would exit after SIGHUP and not reopen a TTY.
> 
> (I have copied the condition from __do_SAK().  That of course doesn't
> mean it's correct.)
> 	Mirek

Right it may be hung_up_tty_read that was what bothered me. I've had a
think through the different scenarios and I can't think of a simple one
where I can abuse this as the vhangup() path is current root triggered
and loses the tty (so I can't reopen on it)

There are more complex questions - what happens when the much needed
revoke() goes mainstream [and we fix all the security issues its lack
causes], and the case where I do

	login on tty1
	login on tty2

On tty1 run a process which sets nohup and causes a vhangup then opens
tty2 while tty2 command line is running some long running program that
doesn't take input that I could plausibly run legitimately (eg a long
complex sql query, or a slow security check etc)

Alan
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