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

From: "Kathleen Moriarty" <[email-masked]>
Date: Thu, 05 Mar 2015 07:22:02 -0800

Kathleen Moriarty has entered the following ballot position for
draft-ietf-bfcpbis-rfc4582bis-13: Discuss

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DISCUSS:
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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.

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COMMENT:
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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.