Re: [bfcpbis] Kathleen Moriarty's Discuss on draft-ietf-bfcpbis-rfc4582bis-13: (with DISCUSS and COMMENT)

[Spencer Dawkins at IETF <[e-mail]>]

Just continuing the trend of ADs talking to each other in ballot threads :-)

On Thu, Mar 5, 2015 at 9:22 AM, Kathleen Moriarty <
[e-mail]> wrote:

> Kathleen Moriarty has entered the following ballot position for
> draft-ietf-bfcpbis-rfc4582bis-13: Discuss
>
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> Please refer to http://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
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> The document, along with other ballot positions, can be found here:
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>
>
>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> Thanks for your work on this draft, it was very well written which is
> much appreciated.
>
> I just have one item I'd like to discuss that should be very easy to
> resolve.
> This should be considered with Spencer's question on what happens when
> the fragments are larger or smaller than the path MTU.  It's important to
> state this to prevent fragmentation overlap attacks (unless you can
> explain why we don't need to worry about that).
>
> In the second sentence on page 42, adding the ending clause may be
> helpful:
>   The size of each of these N messages MUST be
>    smaller than the path MTU to help prevent fragmentation overlap
> attacks.
>
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
>
> Spencer asked what happens when TLS/DTLS is not used, so perhaps
> rewording of the intro to the security considerations section would help
> to clear up his point.  TLS/DTLS is the MTI with flexibility left in to
> support some other undefined mechanism to secure the channel.  Since no
> MTU is set, but recommended, the first few sentences are a bit confusing.
>  The rest of the paragraph is clear in terms of MTI and recommendations
> when TLD/DTLS is used as well as alternates options supporting the listed
> desired security properties.


I think what I was wondering, was whether it's obvious that it's easier to
off-path attack UDP protocols than TCP protocols in general, since an
attacker has to splice attack packets into the TCP sequence numbering,
while UDP doesn't have the same ... I don't want to say "protection", but
maybe "obstacle". So, DTLS is in some sense more helpful than TLS, in
resisting off-path attacks.

Kathleen being the security type that I'll never be, please pay more
attention to her thoughts about this than mine!

Spencer


> Security Considerations
>
>    BFCP uses TLS/DTLS to provide mutual authentication between clients
>    and servers.  TLS/DTLS also provides replay and integrity protection
>    and confidentiality.
>
>
>