Re: [tsvwg] Regarding DTLS and UDP options

[Tom Herbert <[e-mail]>]

On Fri, Apr 14, 2017 at 4:56 PM, Joe Touch <[e-mail]> wrote:
> Hi, all,
>
> Christian Huitema a question about the interaction between DTLS and UDP
> options during my remote presentation at IETF 98.
>
> I took a closer look and consulted with Eric Rescorla (DTLS author). He
> and I agreed as follows:
> - DTLS would currently not cover UDP options; DTLS protects only the UDP
> payload
> - the situation is analogous to TCP options, which are not covered by TLS
> I.e., both TLS and DTLS are transport *payload* security only, despite
> their names.
>
> Christian noted that this may be a reason QUIC prefers UDP (to avoid the
> need to protection transport options), however QUIC does not (and
> cannot) deprecate UDP payloads that are smaller than the IP payload.
> That would require a change to RFC 768.
>
> I'll add a clarification on this point to the next rev of the UDP
> options document.
>
Since the UDP options are not covered by DTLS couldn't that allow a
middleman attacker to add arbitrary UDP options to a packet thereby
potentially circumventing the security provided DTLS? Maybe if DTLS is
in use then AE option should be required also? Note that this case
differs from TCP options since the sender in my example my not even
have a clue as to what UDP options are.

Tom

> Joe
>