full-disclosure - Microsoft Windows and *nix Telnet PortNumber Argument Obfuscation

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Message-ID: <1118357708.9686.168.camel@linux.site>
Date: Thu Jun  9 23:57:13 2005
From: khermans at cisco.com (Kristian Hermansen)
Subject: Microsoft Windows and *nix Telnet PortNumber
	Argument Obfuscation

On Thu, 2005-06-09 at 08:06 -0700, Etaoin Shrdlu wrote:
> For those of us actually looking at it as an
> early warning system, think of Nick as being a vocal representative of the
> majority of more senior security people on the list.

OK.  Fair enough, but at least some people found it "informative".  The
technique described probably does affect many networking tools, as you
stated, but one should ask if this is a proper coding technique or not
(think secure code).  The input does not map to the expected output --
and the user should have been told that the port number is out of range.
Otherwise, what if he thinks 65571 is a valid port after executing that
command?  He may be naive, but shouldn't the telnet programmer let him
know that he is mistaken in his port choice?

As an analogy, it is also true that a C programmer could pull some nice
tricks to optimize his code, but that code may confuse another
programmer trying to understand it.  This is a system, like anything
else, and things are based on give/take.  I don't see why allowing this
to happen actually helps anyone but the telnet programmer -- because it
could confuse many users.  That's my rant and I'm done -- the users who
did not know about this have been informed and that was the point of the
original notice.  My apologies to the "elite", who sit so highly upon
their horses and throw flames down from above ;-)
-- 
Kristian Hermansen <khermans@...co.com>
Cisco Systems, Inc.