SSC-3: Late Letter Ballot comment

Entzel, Paul Paul.Entzel at lsi.com
Wed Apr 2 07:41:17 PDT 2008


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Kevin,
I think you have pointed out a gaping hole in this part of the standard.
There is no definition for the phrase "default data encryption
parameters" anywhere in SSC-3.	I always assumed we had one, since we
used the term several times in the standard, but I went to look for it
as a rebuttal to your email, and it's not there.  This is probably a
common problem when creating such a large proposal, if you remember the
final version of the proposal that added encryption control to SSC-3 was
about 30 pages long.  Anyway, it might help you understand my point of
view if I were to describe my definition of the "default data encryption
parameters".  The default data encryption parameters are a statically
defined set of data encryption parameters as defined in 4.2.21.8 with
the encryption mode parameter set to DISABLE, the encryption mode
parameter set to DISABLE, and the key instance counter parameter set to
0.  All other fields are undefined.  The last sentence fixes the problem
of what to put in the I and the T parameters, and more important, what
to put in the key scope parameter.  In my opinion, it does not matter
what you put in these parameters, since the parameter set is statically
defined, that is, it exists from reset and never gets release or
reallocated.  It is shared between I_T nexuses, like the ALL I_T NEXUS
scope parameters set, but exists even when a valid ALL I_T NEXUS scope
set of data encryption parameters exists.  I like this concept because
it gives you a place to park any I_T nexuses that set a LOCAL scope set
of data encryption parameters that specify DISABLE/DISABLE without
burning a full set of unique data encryption parameters for them.
However, another way to fix this problem would be to remove this term
and add a couple of new rules to the ALL I_T NEXUS scope set of data
encryption parameters.	In the original proposal, support for the the
ALL I_T NEXUS scope was not mandatory, so this would have not fixed the
problem.  But in SSC-3 now, support for this scope is mandatory and in
4.2.21.8 there is a paragraph that states:
A device server shall support an encryption key scope value of ALL I_T
NEXUS and the physical device shall have resources to save one set of
data encryption parameters with this scope.
Since the ALL I_T NEXUS scope set of data encryption parameters is
statically allocated, there's no reason rules can't be created for the
default settings to be used on power-up and when no key of this scope is
defined.  How about if this set of data encryption parameters is defined
to default to DISABLE for the encryption mode and decryption mode
parameters?  A rule could be added that the ALL I_T NEXUS scope data
encryption parameters shall be set to default values when released.  If
you did this, then the term "default data encryption parameters" is
synonymous with the term "set of data encryption parameters with the
scope parameter of ALL I_T NEXUS".  This is true because the default
data encryption scope parameter for each I_T nexus is PUBLIC (see
4.2.21.7).  There are a couple of places that state what to do if there
is no ALL I_T NEXUS scope data encryption parameters that would need to
change, since there always will be one.
Either of these changes will fix the problem of what key instance
counter value to lock to.
As for the UML, I am far from an expert and am a little confused about
your use of DS(1).  However, the information saved per I_T nexus is
defined in 4.2.21.7 and the information saved per data encryption
parameters set is defined in 4.2.21.8, and they are significantly
different.  We've already discussed that there is not always a one to
one relationship between I_T nexus and data encryption parameters, and
that not every I_T nexus will have a set of data encryption parameters
that is "owns".  However, if you agree with the concepts I mentioned
above, there is one and only one set of data encryption parameters
associated with each I_T nexus at all times (a LOCAL set, the ALL I_T
NEXUS set, or the default set (if this concept remains)).
I hope this helps,
Paul Entzel
________________________________
From: Kevin D Butt [mailto:kdbutt at us.ibm.com] 
Sent: Tuesday, April 01, 2008 5:36 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, 
I see. I think I agree with everything you have said. 
My review has uncovered the need to add a statement that the "data
encryption scope" field is set to PUBLIC when the device server
processes a set data encryption page with the SCOPE field set to PUBLIC.
How "key scope" is set to LOCAL is not covered. 
To summarize in a UMLish view what we discussed: 
a.	DS (1)-------(0..1) set of data encryption parameters with key
scope=ALL I_T NEXUS 
b.	DS (1)-------(0..n) set of data encryption parameters with key
scope=LOCAL [there is one for every I_T nexus that has a data encryption
scope=LOCAL] 
c.	DS (1)-------(1..n) saved information per I_T nexus (4.2.21.7)
[there is one for every I_T nexus in existence]
a) and b) are constrained such that only one can exist at a time for a
specific I_T nexus. 
When the data encryption scope=PUBLIC for an I_T nexus, then that I_T
nexus uses the data encryption parameters in a) if they exist. 
Now my concern is, what is the proper behavior in this scenario: 
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, the ENCRYPTION MODE field set to DISABLE and
DECRYPTION MODE field set to DISABLE or RAW. 
According to 4.2.21.6 If the encryption/decryption modes are set to
DISABLE, then "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;" 
I believe the intent would be to lock B to the encryption parameters for
the ALL I_T NEXUS (i.e., established by A).   
But if there were no A, then what would happen?  There are no encryption
parameters (..shall release any resources that it had allocated to store
data encryption parameters..) so there is no "key instance counter". 
I think it would break if the key instance counter were released.
Instead the key instance counter should be incremented.  This needs to
be corrected. 
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> 
04/01/2008 02:48 PM 
To
Kevin D Butt/Tucson/IBM at IBMUS 
cc
"Ballard, Curtis C \(StorageWorks\)" <curtis.ballard at hp.com>,
<owner-t10 at t10.org>, <t10 at t10.org> 
Subject
RE: SSC-3: Late Letter Ballot comment
Kevin, 
The device server should not establish a set of data encryption
parameters for an I_T nexus that issues a SPOUT command that sends a Set
Data Encryption page with the SCOPE field set to PUBLIC.  See the third
paragraph in 4.2.21.7.	There is no question that this could be made
clearer both in the model clause and in table 142. 
Paul 
________________________________
From: Kevin D Butt [mailto:kdbutt at us.ibm.com] 
Sent: Tuesday, April 01, 2008 1:48 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
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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