Re: PFinger 0.7.8 format string vulnerability (#NISR16122002B)

[Valdis.Kletnieks () vt edu]

On Mon, 16 Dec 2002 21:39:32 +0100, Stefan Esser <s.esser () e-matters de>  said:
> Hello,
>
> > Due to the way requests are logged the only way to exploit this
> > vulnerability is through setting the DNS name of the fingering host to the
> > attacker supplied format string.
>
> I really wonder how you want to exploit this... Last time I checked
> all tested resolvers (Linux/BSD/Solaris) did not allow % within domain
> names and so your format string vulnerability is not exploitable at all...

Gotta read them RFC's carefully. ;)

*ON THE WIRE*, all 256 byte codes are legal, since DNS uses a length-data
encoding.  Currently, there's restrictions on what chars are legal *for use*,
but there's no reason to suppose that with i18n and UTF-8 possibly appearing in
domain names, this will change.

Now ponder the fun you can have with a PTR entry - as that is what needs to
be returned for "setting the DNS name of the fingering host".  What? You can't
get that into a BIND 9 zone file?  Try grepping through the source
for "check-names" and ponder the possibilities.  You don't even need to
hack the source code for this one....
-- 
                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                Virginia Tech

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