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

[Kathleen Moriarty <[e-mail]>]

Hi Paul,

I think we are close, thanks for your response.  Inline.

On Wed, Sep 23, 2015 at 2:26 AM, Paul E. Jones <[e-mail]> wrote:
> Kathleen,
>
> Following up on this email (and building a growing to-do list)....
>
>
> ------ Original Message ------
> From: "Kathleen Moriarty" <[e-mail]>
> To: "The IESG" <[e-mail]>
> Cc: [e-mail]; [e-mail];
> [e-mail]; [e-mail]
> Sent: 3/5/2015 10:22:02 AM
> Subject: [bfcpbis] Kathleen Moriarty's Discuss on
> draft-ietf-bfcpbis-rfc4582bis-13: (with DISCUSS and COMMENT)
>
>> 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).
>
>
> Are you concerned about IP-packet level fragmentation overlap or payload
> level fragmentation overlap issues?  I think the former should be addressed
> with "do not fragment IP packets".  The latter is an area that is not
> addressed in the spec at present.  However, if there is overlap in the
> application data, I do not see any harm.  Of course, it would be important
> to check to ensure lengths are all correct to prevent buffer overruns.
>
> Am I missing something here?

I think we are good with the agreed text below on this point.
>
>
>> 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.
>
>
> This would be a good addition.  We have other text we need to add re: path
> MTU and it is the intent that all messages fit within the path MTU.

Thanks, please let me know when this has been added to the draft and
I'll clear.  I see a -14 was posted, but don't see this text and could
have missed it.  If so, a pointer would be helpful.

>
>
>> ----------------------------------------------------------------------
>> 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.
>>
>> Security Considerations
>>
>>    BFCP uses TLS/DTLS to provide mutual authentication between clients
>>    and servers.  TLS/DTLS also provides replay and integrity protection
>>    and confidentiality.
>
>
> At present, TLS/DTLS are recommended, but not mandatory.  Without them,
> there is a host of attacks one could perform against either a client or
> server, especially over UDP, and there is no authentication or
> confidentiality.  Much of that is spelled out in the security considerations
> section.

Aren't they mandatory to implement (MTI), but not mandatory to use
(MTU)?    The "recommended" in the security considerations , I thought
could go further since you have an MTI, no?  The request would be a
slight rewording of the introduction or an explanation of why
recommended is appropriate even though there is an MTI.  In full
disclosure, I read this in full when the discuss was placed, but just
skimmed the applicable sections this time, so I may have missed
something.

Thanks,
Kathleen

>
> I apologize, but I'm missing what your request is here.  Can you clarify for
> me?
>
> Paul
>



-- 

Best regards,
Kathleen