Re: TCP Sack processing

[snort user <snort.user () gmail com>]

Joachim,

The TCP stream reassembly algorithm usually handles out-of-order packets.
So if the packets comes in the order P1, P3, P2 it will be correctly
reordered and reassembled.

Thanks

On 8/11/05, Joachim Schipper <j.schipper () math uu nl> wrote:
> On Tue, Aug 09, 2005 at 04:28:10PM -0400, snort user wrote:
> > Greetings.
> >
> > Does TCP stream reassembly algorithm need TCP SACK processing for completeness ?
> > Are there scenarios that an IDS/IPS would miss an attack if it does
> > not take the selective acks into consideration.
> >
> > Any comments/opinions/pointers is appreciated.
> >
> > Thanks
>
> Well, I am not an expert, but...
>
> Suppose I have an exploit that requires a TCP connection. I open the
> connection, send packet #1 and #3, and then sent #2 after #3 has been
> SACK'ed. Wouldn't that work, and bypass your IDS, especially if the
> exploit is divided over the packets in a smart way?
>
>                 Joachim
>
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