SSC-3: Late Letter Ballot comment
Kevin D Butt
kdbutt at us.ibm.com
Tue Apr 1 12:47:42 PDT 2008
Formatted message: <A HREF="r0804015_f.htm">HTML-formatted message</A>
My comments below <<kdbutt>>
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 at us.ibm.com
http://www-03.ibm.com/servers/storage/
"Entzel, Paul" <Paul.Entzel at lsi.com>
Sent by: owner-t10 at t10.org
04/01/2008 06:51 AM
To
Kevin D Butt/Tucson/IBM at IBMUS
cc
"Ballard, Curtis C \(StorageWorks\)" <curtis.ballard at hp.com>,
<t10 at t10.org>
Subject
RE: SSC-3: Late Letter Ballot comment
Kevin,
Comments below.
Paul Entzel
From: Kevin D Butt [mailto:kdbutt at us.ibm.com]
Sent: Monday, March 31, 2008 5:21 PM
To: Entzel, Paul
Cc: Ballard, Curtis C (StorageWorks); owner-t10 at t10.org; t10 at t10.org
Subject: RE: SSC-3: Late Letter Ballot comment
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.
[Paul Entzel] Yes.
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).
[Paul Entzel] The fist half of this sentence is correct, but the
parenthetical part is not. In my example, initiator A established a set
of shared data encryption parameters using the ALL I_T NEXUS scope.
Initiator B did not establish a set of parameters, but instead created an
association with the shared data encryption parameters and locked itself
to this set of parameters by using the PUBLIC scope and the LOCK bit. The
two initiators are associated with the same set of data encryption
parameters.
<<kdbutt: Yes, because B used PUBLIC it refers to the ALL I_T NEXUS
parameters. I missed this.>>
The key point here is that the encryption parameters are set per I_T
nexus.
[Paul Entzel] If this were true, Curtis' external encryption control will
never work. If the scope is LOCAL, then this is true. If the scope is ALL
I_T NEXUS, then the data encryption parameters are shared between the I_T
nexus that set them and all I_T nexuses that have been configured with a
scope of PUBLIC.
<<kdbutt: I agree>>
Any changes that occur on other I_T nexuses do not change the parameters
in another I_T nexus.
[Paul Entzel] If the SCOPE field is LOCAL in page that establishes a set
of data encryption parameters, then this is generally true. To
accommodate designs with limited resources for storage of data encryption
parameters (particularly keys), the standard allows for the device to
release a set of data encryption parameters for anther I_T nexus when they
needed to establish a new set of data encryption parameters for a
different I_T nexus. This feature is optional. See the second paragraph
in 4.2.21.8. Remember, the data encryption parameters are not IN the I_T
nexus, they are in the physical device. They are owned by an I_T nexus
and possible shared with other I_T nexuses.
<<kdbutt: I agree>>
This means the LOCK bit only helps the I_T nexus that set the encryption
parameters with the LOCK bit set.
[Paul Entzel] The LOCK bit only applies to an I_T nexus that set the bit
in the Set Data Encryption Parameters page in the last SPOUT command that
sent this page.
<<kdbutt: I agree>>
This page may not have established a set of data encryption parameters, it
may have also had the SCOPE field set to PUBLIC which means that the I_T
nexus is locked to the current set of ALL I_T NEXUS data encryption
parameters, if one exists.
<<kdbutt: In this case there is a set of data encryption parameters. The
key scope and the encryption mode and decryption mode are all part of the
data encryption parameters. This means that when the SCOPE is set to
PUBLIC, that there exists data encryption parameters associated with this
I_T nexus, but it also means that this I_T nexus is to use the data
encryption parameters that are set with a SCOPE of ALL I_T NEXUS. This
means that this I_T nexus has two sets of data encryption parameters - the
one whose scope is PUBLIC and the one whose scope is ALL I_T NEXUS.
In 4.2.21.7 paragraphs 3,4,5, and 6 the scope is referred to as being
saved by I_T nexus. But in 4.2.21.8 key scope is listed as part of the
data encryption parameters. How can data encryption parameters not be by
I_T nexus yet some of its members are by I_T nexus. I think this shows
that the requirements are not clear in SSC-3. I agree that data
encryption parameters should be a global thing, but some of what we list
as data encryption parameters are said to be for a specific I_T nexus.
Perhaps I am looking at this wrong, but it seems to be lacking a complete
or concise description and we have placed certain parameters in the data
encryption parameters when we should not have.>>
If not, it is locked to the default set of data encryption parameters
(DISABLED/DISABLED).
The point behind the LOCK bit was to provide a method to prevent the
device from writing data if the data encryption parameters had changed
since the last time the application client configured them without the
application client having a chance to fix them again, even in an
environment where UAs don't make it to the proper layer to fix the
problem. If Gideon is listening, this is the place where he jumps in and
claims that the protection is too weak and so it is worthless, but it is
what we have.
<<kdbutt: I agree with the point of the LOCK>>
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 at us.ibm.com
http://www-03.ibm.com/servers/storage/
"Entzel, Paul" <Paul.Entzel at lsi.com>
Sent by: owner-t10 at t10.org
03/31/2008 02:55 PM
To
"Ballard, Curtis C \(StorageWorks\)" <curtis.ballard at hp.com>,
<t10 at 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 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Ballard,
Curtis C (StorageWorks)
Sent: Monday, March 31, 2008 2:51 PM
To: 't10 at 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 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Kevin D
Butt
Sent: 20 March 2008 21:48
To: t10 at 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 at us.ibm.com
http://www-03.ibm.com/servers/storage/
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