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

[Kathleen Moriarty <[e-mail]>]

Sent from my iPhone

> On Mar 5, 2015, at 11:14 AM, Spencer Dawkins at IETF <[e-mail]> wrote:
> 
> 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
>> 
>> When responding, please keep the subject line intact and reply to all
>> email addresses included in the To and CC lines. (Feel free to cut this
>> introductory paragraph, however.)
>> 
>> 
>> Please refer to http://www.ietf.org/iesg/statement/discuss-criteria.html
>> for more information about IESG DISCUSS and COMMENT positions.
>> 
>> 
>> The document, along with other ballot positions, can be found here:
>> http://datatracker.ietf.org/doc/draft-ietf-bfcpbis-rfc4582bis/
>> 
>> 
>> 
>> ----------------------------------------------------------------------
>> 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.
> 

Interesting, it would be good to understand this as well.  Thanks for catching this and raising the question.

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

Spencer is humble, please do answer his questions as well!

Thanks,
Kathleen
> 
> 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.
>