To: roweber@IEEE.org, Black_David@emc.com Cc: t10@t10.org Subject: Re: SA Usage Leakage From: Kevin D Butt <kdbutt@us.ibm.com> Date: Fri, 7 Nov 2008 14:50:36 -0700 X-Message-Number: 9280 Formatted message: HTML-formatted message Ralph, As I understand it, the SA state is not tied to one initiator or another. Once it is created it uses the SAI to determine which SA to use. There is no way to determine if it was another initiator that caused the info to be cleared. This is a whole new concept where the item in question (the SA) is not tied to any I_T nexus. Creating a UA for removing SA state information is not a good idea. In fact it could lead to all applications out there checking to see if the SA they are using is still available. This does not make sense to me. In fact, SPC-4 already states that if the SA Timer expires the state information is discarded and there is no mention of creating a UA - thankfully. This situation is only slightly different. We still believe that: 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 (not just 5/2600 pointing to the SA field) 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/ From: Ralph Weber <roweber@IEEE.org> To: t10@t10.org Date: 10/31/2008 06:55 PM Subject: Re: SA Usage Leakage Kevin, Why is it better to have to define, establish, etc. a UA for SA CLEARED BY ANOTHER USER than to simply refuse to do that which cannot be done? Do not for a minute think that SCSI is going to allow SAs to be discarded without establishing a UA. That is simply not done. Either way there is a messy Denial of Service problem: UAs out the ying-yang or full frontal request rejection. Think about it! All the best, .Ralph Kevin D Butt wrote: I sent out a note on SA Usage Leakage a while back and then lost track of this item. David Black responded with "I don't see a problem with this in principle. The original IKEv2 allows state to be discarded at will." The original note is: =========== 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 =========== Also there should be a high-level statement/behavior in the usage model about attempts to use an unknown SA (not just 5/2600 pointing to the SA field). Does anybody disagree with this or agree that this would be a good thing to do? 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/