Re: OBSD reaction to CERT advisory

[Daniel Hartmeier <daniel () benzedrine cx>]

On Wed, Oct 09, 2002 at 09:27:12AM -0400, Paul D. Robertson wrote:

> http://www.kb.cert.org/vuls/id/AAMN-5EQPEF

Part of that statement is a quote from an (internal) email I sent in
reply to the question whether OpenBSD was vulnerable. That explains the
undiplomatic choice of words.

The reason IPFilter is referenced is the fact that OpenBSD did ship with
this packet filter prior to release 3.0, hence I think the vendor
statement should include this distinction.

> Statements like "The problem is in ipf" when there's been zero 
> actual verification, let alone communication with the author should be 
> taken as disinformation.

Look at the source, it's obvious that selective ACK retransmissions
fool the in-kernel ftp proxy. I don't think it's necessary to provide an
actual exploit to proof the vulnerability. If, after reading the source,
you don't agree that IPFilter, in a configuration where the in-kernel
ftp proxy should protect the ftp _server_, is vulnerable to this kind of
attack, let me know.

I strongly believe that placing any application level proxy at the
packet filter layer is fundamentally flawed.

Daniel
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