large organization nameservers sending icmp packets to dns servers.
jabley at ca.afilias.info
Wed Aug 8 16:15:44 UTC 2007
On 8-Aug-2007, at 11:59, Jamie Bowden wrote:
> I have a question related to what you posted below, and it's a pretty
> simple one:
> How is answering a query on TCP/53 any MORE dangerous than
> answering it
> on UDP/53? Really. I'd like to know how one of these security
> justifies it. It's the SAME piece of software answering the query
> either way.
There are people (I believe; this is a little rumour-laden) who take
the approach that 53/tcp is actually safer than 53/udp, since the
handshake makes it easier to believe the query's source address. The
approach I heard about was to reply to UDP-transport queries with
some minimal answer set with TC set, and serve a more useful set of
information over TCP once the re-query arrives.
[I realise that the state involved in handing TCP queries on a busy
server is non-trivial, and that there are many aspects to this
approach which deserve raised eyebrows.]
However, my point is that "TCP is more secure than UDP" also has a
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