Re: Linux 2.4.27 SECURITY BUG - TCP Local and REMOTE(verified) Denial of Service Attack

Willy Tarreau
2004-09-13T19:18:28Z

On Mon, Sep 13, 2004 at 09:07:41PM +0200, Tonnerre wrote:
> Salut,
>
> On Mon, Sep 13, 2004 at 06:18:47AM +0200, Willy Tarreau wrote:
> > > The BGP state machine should instead, in normal operation, have
> > > only treated Hold time expired as the definitive sign of "peer is
> > > down" and allowed reconnects.
> >
> > It should not necessarily wait for the time-out, but at least wait for
> > a few reconnect errors.
>
> Problem there: you can fake connection errors almost as easily as
> sending an RST packet, so the DoS might reappear, might it not?
>

No, as long as you don't keep the routes from the old session until the
new one establishes and fills up (or you reach the timeout). And when I
spoke about "connection errors", I really spoke about connection
establishment. I bet you'll have more difficulties trying to send the
right RST just after a SYN (or an ICMP unreachable with the right payload)
than sending them once the session is already established. It does make
a big difference.

Willy