On Mon, Apr 27, 2015 at 05:15:32PM +0200, Simon Josefsson wrote:
> Ilari Liusvaara <[email protected]> writes:
> 
> > - Does DNS-over-DTLS need some sort of channel identifier in queries
> >   (taking place of the 5-tuple)? To deal with things like client IP
> >   address/portrange changes or client socket being dropped[1].
> 
> If I understand correctly, I don't believe DTLS has this, nor that it is
> something you want -- if something is messing with the traffic, you
> wan't detect/reject it not work around it.

This is about dealing with things like:
- ISP suddenly renumbering connection.
- NAT dropping state.

The DTLS itself does not specify how to associate packets with
connection state.

Some of the ways seen: 5-tuples, in-band connection identifiers, out-
of-band designation.

> > Also, some problems with (D)TLS:
> > - No length hiding: There is no defined mechanism for length hiding
> >   (which is needed unless one can pad at DNS level). I think there
> >   have been at least one proposal tho.
> 
> (D)TLS has message padding to mitigate packet length analysis.
> Addmittedly, you can't pad more than 255 bytes.

Only in block modes, which have number of problems (Chrome actually
warns about "obsolete cryptography" if those are used).


-Ilari

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