Discouraging use of network-writable data

This email is about the second major issue discussed in San Diego.
Here's the summary of the potential attack from the draft minutes:

  Issue is around having data sink buffer contents getting changed
  before the buffer [STag] is invalidated.  If protocol or
  application logic depends on the contents not changing, this may
  open up attacks on the protocol.  IPsec doesn't help because one
  has to protect against a less than fully trusted peer who can
  authenticate and use IPsec if required.

Requiring all Stags to be One-Shot (single RDMA operation) has
been discussed and rejected on the list.  Discussion in San Diego
reinforced that rejection.  I believe that rejection is the
rough consensus of the RDDP Working Group.

Two approaches beyond stiff warnings to ULP implementers were
discussed in San Diego.  This is slightly summarized from the
minutes:

  a) Receive and Invalidate.

  Problem: This won't work when data transfers can complete in
	non-deterministic order, because the exact sequence of
	completion has to be known in advance.  Both iSCSI and
	NFS exhibit this non-deterministic order behavior.

  Sense of room: Not worth pursuing further due to limited
	applicability.

b) RDMA Write & Invalidate:

  Defining RDMA Writes that do and don't invalidate the
  appropriate STag still requires a receiver check for
  invalidation and hence provides no leverage.

  Sense of room: Not worth pursuing.

  Conclusion of issue: Need to make sure security and protocol
  drafts contain stiff warnings about the need for any ULP using
  RDDP to invalidate receive STags prior to using data they cover.

This is an opportunity for anyone on the list to object to
the conclusions from the San Diego meeting, but please read
the entire San Diego minutes on this topic before objecting.

Thanks,
--David

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David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email protected]        Mobile: +1 (978) 394-7754
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