More ESP-SCSI issues

Kevin D Butt kdbutt at us.ibm.com
Mon Apr 7 09:30:27 PDT 2008


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Everybody undoubtedly knew more issues would be found with the new 
security stuff.  We have found two more items.	The first needs 
clarification, the second, seems like we just did a bad thing with the 
March approved, 08-158r1.
Issue #1:
The second to last paragraph on page 163 of SPC-4r14:
If the DS_SQN SA parameter is equal to FFFF FFFF FFFF FFFFh, the device 
server shall delete the SA.
<<kdbutt: There is confusion about this statement.
First, I believe that there is an assumption that the ICV is correct, that 
should be stated.
Second, does the deletion occur after processing the command or do you not 
process the command and just delete the SA?
Third, should this be at the end of the section following this paragraph?
---> page 164, SPC-4r14: If the command is not terminated due to a 
sequence number error or a mismatch between the computed integrity
check value and the contents of the INTEGRITY CHECK VALUE field, then the 
device server shall copy the contents of
the received DS_SQN field to its DS_SQN SA parameter.<---
Fourth, should the converse be added to item c) above the paragraph "c) 
The value in the DS_SQN field is greater than 32 plus the value in the 
device server?s DS_SQN SA parameter and if the DS_SQN SA parameter is not 
equal to FFFF FFFF FFFF FFFFh."
Fifth, it seems weird to delete the SA here.  What is the thinking or 
justification for this?  Is it intended to happen only when there is a 
failure?
>>
Issue #2:
The new reserved field was placed between two values used in generating 
the AAD field used for ICV.   A lot of algorithms expect it to be a flat 
buffer (i.e., contiguous).  With the new reserved fields there is a gap. 
This would disallow generating as the buffer is being built.
Table 70 and 71 (and 75 and 76) have the SAI and SQN contiguous with 
reserved fields before them.  Tables 72 and 73 (and 77 and 78) have a gap 
between SAI and SQN with that gap being the new reserved bytes. 
SUGGESTED FIX: The reserved bytes should be before the SAI and SQN. 
pg 164 of SPC-4r14 describes how the SAI and SQN fields are used.:
===============
If the integrity algorithm for the SA specified by the DS_SAI field is 
AUTH_COMBINED (see 5.13.7.2), then the AAD
input to the encryption algorithm is composed of the following bytes, in 
order:
1) The bytes in the DS_SAI field; and
2) The bytes in the DS_SQN field;
The INTEGRITY CHECK VALUE field contains a value that is computed as 
follows:
a) If the integrity algorithm is not AUTH_COMBINED, the integrity check 
value is computed using the
specified integrity algorithm with the following bytes as inputs, in 
order:
1) The bytes in the DS_SAI field;
2) The bytes in the DS_SQN field;
3) The bytes in the INITIALIZATION VECTOR field, if any; and
4) The bytes in the ENCRYPTED OR AUTHENTICATED DATA field after 
encryption, if any, has been performed;
or
b) If the integrity algorithm is AUTH_COMBINED, the integrity check value 
is computed as an additional
output of the specified encryption algorithm.
================
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



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