To: "Entzel, Paul" <Paul.Entzel@lsi.com>
Cc: "Ballard, Curtis C \(StorageWorks\)" <curtis.ballard@hp.com>,
owner-t10@t10.org, t10@t10.org
Subject: RE: SSC-3: Late Letter Ballot comment
From: Kevin D Butt <kdbutt@us.ibm.com>
Date: Mon, 31 Mar 2008 16:20:55 -0700
X-Message-Number: 8670
Formatted message: HTML-formatted message
Paul,
Just to be clear, the LOCK bit is only associated with the specific I_T
nexus on which the SPOUT command was received with the LOCK bit set. In
your example A is not locked to the parameters (the parameters being those
set for I_T nexus A) but B is locked to the parameters (those parameters
set for I_T nexus B - which are different parameters than those that are
set for I_T nexus A).
The key point here is that the encryption parameters are set per I_T
nexus. Any changes that occur on other I_T nexuses do not change the
parameters in another I_T nexus. This means the LOCK bit only helps the
I_T nexus that set the encryption parameters with the LOCK bit set.
Thanks,
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt@us.ibm.com
http://www-03.ibm.com/servers/storage/
"Entzel, Paul" <Paul.Entzel@lsi.com>
Sent by: owner-t10@t10.org
03/31/2008 02:55 PM
To
"Ballard, Curtis C \(StorageWorks\)" <curtis.ballard@hp.com>,
<t10@t10.org>
cc
Subject
RE: SSC-3: Late Letter Ballot comment
Hello Curtis,
The concept of LOCK was to allow an I_T nexus to create a fixed
association with a particular set of data encryption parameters at a
specific generation (key instance counter). This association is saved
with the I_T nexus (see subclause 4.2.21.7) not with the set of data
encryption parameters because more than one I_T nexus can be associated
with a set of data encryption parameters (one as the creator, others using
the PUBLIC scope). It was not an oversight to not include the lock bit in
the data encryption parameters structure, it doesn't belong there.
Consider the example where I_T nexus A sends a SPOUT command to create a
set of data encryption parameters with a scope of ALL I_T_NEXUS but does
not set the LOCK bit, then I_T nexus B sends a SPOUT command with a scope
of PUBLIC with the LOCK bit set to 1. In this example, A is not locked to
the parameters but B is. What would you put in the lock parameter if it
was part of the set of data encryption parameters?
You may want to consider fixing the problem by introducing the concept of
a master key instance counter in 4.2.41.10 that is not associated with any
set of data encryption parameters. It would be incremented and inserted
into the set of data encryption parameters each time one is created. You
would also need to modify the test in 4.2.21.11 such that a lock violation
occurs if the I_T nexus is locked and the data encryption parameters have
been released.
Paul Entzel
From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Ballard,
Curtis C (StorageWorks)
Sent: Monday, March 31, 2008 2:51 PM
To: 't10@t10.org'
Subject: RE: SSC-3: Late Letter Ballot comment
Kevin,
I looked into this a bit and came to a different conclusion.
You reference section 4.2.21.6 on Managing keys within the device server
and the section on when to release a set of data encryption parameters
which does not discuss turning off encryption.
I believe the section we need to reference is a little further into
4.2.21.6 at that start of document page 56 in SSC3r04a.pdf where it
discusses what to do when both the ENCRYPTION MODE and the DECRYPTION MODE
are set to DISABLE which is the encryption off condition.
"If a device server processes a Set Data Encryption page with the
ENCRYPTION MODE field set to DISABLE and DECRYPTION MODE field set to
DISABLE or RAW, the physical device shall:
a)release any resources that it had allocated to store data encryption
parameters for the I_T nexus associated with the SECURITY PROTOCOL OUT
command and shall change the contents of all memory containing a key value
associated with the data encryption parameters that are released; and
b)establish a unit attention condition . . ."
The statement "data encryption parameters" was referenced to 4.2.21.8
earlier in that clause so if we follow that reference we find that
virtually all of the settings that a host can establish are included in
the data encryption parameters including the key instance counter which is
tied to locking. When both modes are set to DISABLED which is what has to
be done to turn encryption off, then everything in the set of data
encryption parameters is released so all of those values are gone. If the
counter is gone along with all the other parameters I don't see how the
parameters can possibly continue to be associated with that I_T nexus.
According to my notes we discussed at the last SSC-3 meeting that "LOCK"
should also be included in the data encryption parameters but wasn't due
to an oversight. If it had been then it would be clear that "LOCK" is
gone when the encryption parameters are released.
I'm concerned that this behavior seems to be inconsistent with the
introduction to 4.2.21.11 which discusses exactly the case of resources
being released and the UA not detected and suggests that LOCK solves the
issue.
If the intent is that LOCK persist when the rest of the parameters are
released then I don't think the change is as simple as you suggest. I
think that we would need to modify 4.2.21.6 to indicate that the key
instance counter is not released with the rest of the parameters if LOCK
is set to one, but instead is incremented. That way the test described in
the section on locking where a changed key instance counter triggers the
CHECK CONDITION will still work. We might also have to modify some text
describing releasing resources when limited resources are exhausted to
make it clear that parameters containing a LOCK bit set to one can't be
released (I have some concerns with whether that can be required). There
might also be other sections that talking about releasing parameters that
would need examined.
This one looks to me like it's going to take a proposal to address.
Curtis Ballard
Hewlett Packard
From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Kevin D
Butt
Sent: 20 March 2008 21:48
To: t10@t10.org
Subject: SSC-3: Late Letter Ballot comment
I received communication from an ISV today related to Encryption mode
locking (4.2.21.11). They were unable to determine if the locking applied
when the data encryption parameters were set such that
encryption/decryption is turned off. In a close reading this clause
refers to "...locked to that set of data encryption parameters and key
instance counter value until a hard reset condition occurs or another
[SPOUT command is received]"
In 4.2.21.6 Managing keys within the physical device, where it describes
when to release a set of data encryption parameters, there is no mention
of turning off encryption. Therefore, the locking does apply to the saved
set of encryption parameters even when encryption is turned off. This is
indeed the desired behavior. However, it is not clear to the casual or
novice standards reader that this is the case.
Proposed Solution (Editorial):
In 4.2.21.11, p2, add a new sentence after s1:
The LOCK bit in the Set Data Encryption page is set to one to lock the I_T
nexus that issued the SECURITY PROTOCOL OUT command to the set of data
encryption parameters established at the completion of the processing of
the command. A set of data encryption parameters are established and
locked even if the ENCRYPTION MODE is set to DISABLE and the DECRYPTION
MODE is set to DISABLE.
Thanks,
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt@us.ibm.com
http://www-03.ibm.com/servers/storage/