SA Usage Leakage
Kevin D Butt
kdbutt at us.ibm.com
Tue Apr 1 09:47:54 PDT 2008
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We have concerns related to SA usage leakage. That is, it is possible for
application clients to create enough SA's in a device server - with the
timeout values long enough - that the device server is out of resources to
create another. While the answer seems obvious - allow the device server
to implicitly abandon an SA for vendor-specific reasons, there is no
explicit mention of this in SPC-4 that we can find. If the DS is not
allowed to implicitly abandon an SA, the opens up the avenue for Denial of
Service attacks - an attacker could use up all the SA resources with
maximum timeout values.
Key points being:
A) the DS needs to be able to clear space for a new SA
B) no notification of lost SA should be reported to AC until the AC
attempts to use an SA
C) the expected behaviors of the DS and the AC should be explicitly stated
in SPC-4 and be general (i.e., not tied to each usage defined (e.g.,
ESP-SCSI))
D) There should be a unique additional sense code for when an attempt to
use an unknown SAI is made
Please provide comments as we will be driving to a proposal to make this
happen.
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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