Re: Linux 2.2.x ISN Vulnerability

Alan Cox (alan@lxorguk.ukuu.org.uk)
Sun, 26 Sep 1999 19:37:21 +0100 (BST)


> I agree, using known data (port numbers, addresses) as "secret" data to
> hash is false. Instead a good PRNG should be used everytime a sequence
> number is needed, independent to any TCP data. Operating systems such as
> OpenBSD do have cryptographical safe Sequence number generators, why
> should Linux go the unsafe way ?

You can't just use a random number generator. There are _strict_ rules about
sequence spaces keeping ordering. Otherwise your risk data corruption.

> old protocol suites. TCP Sequence numbers were never meant to be secure, a
> 32 bit number just cannot guarantee security at all. Later when the first
> spoofing vulnerabilities were discovered the reasons of the sequence
> number shifted from a "to order data" meaning to a "guarantee security"
> meaning.

Correct. You should be using encrypted IP. Unfortunately the US government
still puts its paranoia before its people's safety

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