IP hack theorizing

[david at thekramers.net (David Kramer)]

Tom Metro wrote:
> Jerry Feldman wrote:
>> David Kramer <david at thekramers.net> wrote:
>>> The IP envelope contains the total length of the datagram.  What would
>>> happen if that number were larger or smaller than the real length?
>>
>> I think the network layer in most implementations has been purged of
>> buffer overflow issues. Most likely, the affected packet would simply
>> be discarded...
> 
> Or corrected. I believe modern software firewalls, like iptables,
> perform a number of sanity checks on packets before they hit the kernel.
> For example, here's a recent log entry triggered by iptables when it
> didn't like the window size specified in a packet:
> 
>  ... TCP: Treason uncloaked! Peer 192.168.0.200:873/59982 shrinks window
> 1150916075:1150916611. Repaired.

Spectacularly cool!  Thanks.

BTW, I'm in the process of asking whether I can publish the paper here.
 There's nothing earth-shattering that real sysadmins don't already
know, but it might be useful for the home users.


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