Messages in this thread | | | Date | Mon, 22 Dec 1997 11:00:11 +1100 | From | Kevin Lentin <> | Subject | Re: Emergency shutdown feature |
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On Sun, Dec 21, 1997 at 11:16:13AM -0500, linux kernel account wrote: > I see the only need for the 'challange system' is so that you can > idenitify the sender. My main difficulity with the challange system, is > that the reboot packet is to reboot a runaway computer. The challange > system would mostlikely lower it's effectiveness. > > Furthermore, there is no need to use a random number to prevent replay. > The window is small enough (4minutes, someone with the ablity to sniff > could do more damage then making it go down again as soon as it came up)..
Also, if you're rebooting a runaway computer, you're likely to take a few minutes to reboot and fsck. A few gig of heavily used disk can suck up time in fsck quite nicely. And if you're really worried (and the loss of 4 minutes is worth less to you than the risk of attack) then put a 4 minute pause in your startup scripts in the case of 'unclean' reboots. Or do not accept 'reboot' packets during the first 4 minutes of uptime (less boot time would probably only be a minute or two at max on a small disk system).
> > - A single valid packet can be replayed until it is no longer valid. > > so your poor host will be rebooting until the packet expires... So > > if you validly reboot the machine, anyone listening can reboot the > > machine for a few minutes... > You couldn't reboot it until it was on the network.. How many > times could I reboot your computer in that 256second window? Maby one > additional time...
Exactly.
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