iSCSI: Proxies (was Security in iSCSI)

[Black_David@emc.com]

Julian,

> You seem to missing my main point. I am ready to take out the
> table but not the general notion of a cryptographic digest.
> To do the later I have to have the community understand that 
> their are left with no protocol provided means to authenticate
> data that pass through iSCSI proxies.

Actually, I was hoping that you weren't going there.  Just when
one thinks one has obtained a good understanding of a network
technology/protocol/solution/etc., adding the notion of proxies
is almost certain to restore the previous state of confusion.
Multicast also has this property, but fortunately, I haven't
seen anyone in the WG take any serious interest in it (and
woe betide anyone who takes this as an invitation ;-) ).

My primary concern is one of schedule - if full support for
proxies is a requirement for the first version of the iSCSI
RFC, the schedule guesstimate I posted yesterday is probably
optimistic by 6+ months.  Issues that come up in the area of
proxies that will take a while to resolve will likely include:

- What's the right scope of proxy support?  How much
	consideration for SCSI level proxies to which other
	transports needs to be reflected in the iSCSI standard?
- SCSI is not an end-to-end transport independent protocol.
	T10 had the opportunity to go in this direction in the
	SCSI GPP work) and chose not to do so. Extensive iSCSI
	work on proxies risks running into SCSI architecture,
	and our experience with ACA suggests that they'll take
	a while to resolve.
- Security interaction with proxies is a very complicated
	subject.  IPsec and NATs is a well-known tarpit that
	is finally getting resolved years later.  I hesitate
	to promise that the iSCSI proxy issues will be significantly
	simpler by comparison.
- There is precedent for proxies adapting to the requirements
	of protocols - TLS requires http proxies to accommodate
	it rather than the other way around.  Whether proxies
	should drive iSCSI security architecture or iSCSI
	security architecture should drive proxy design will
	at the minimum be fodder for serious debate.

If we want to get the iSCSI spec done in a reasonable timeframe,
I suggest closing the lid on this Pandora's box labeled
"proxies" and deferring serious work on iSCSI proxy support
to a future revision.  The separate header and data CRCs are a
useful step towards making life better for those who want to
build proxies, but I hesitate to go much further in that
direction, particularly in the area of security.  As things
currently stand, one way to authenticate data passing through
an iSCSI proxy is to have the iSCSI proxy participate in the
authentication which seems like an acceptable situation (and
one that has a straightforward security explanation).

Comments?

Thanks,
--David
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David L. Black, Senior Technologist
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