Hi, On Thu, Jun 29, 2017 at 1:19 PM, Horia Geantă <horia.geanta@xxxxxxx> wrote: > On 6/28/2017 4:42 PM, Horia Geantă wrote: >> On 6/28/2017 4:27 PM, David Gstir wrote: >>> Certain cipher modes like CTS expect the IV (req->info) of >>> ablkcipher_request (or equivalently req->iv of skcipher_request) to >>> contain the last ciphertext block when the {en,de}crypt operation is done. >>> This is currently not the case for the CAAM driver which in turn breaks >>> e.g. cts(cbc(aes)) when the CAAM driver is enabled. >>> >>> This patch fixes the CAAM driver to properly set the IV after the >>> {en,de}crypt operation of ablkcipher finishes. >>> >>> This issue was revealed by the changes in the SW CTS mode in commit >>> 0605c41cc53ca ("crypto: cts - Convert to skcipher") >>> >>> Cc: <stable@xxxxxxxxxxxxxxx> # 4.8+ >>> Signed-off-by: David Gstir <david@xxxxxxxxxxxxx> >> Reviewed-by: Horia Geantă <horia.geanta@xxxxxxx> >> > Btw, instead of updating the IV in SW, CAAM engine could be programmed > to do it - by saving the Context Register of the AES accelerator. > > Unfortunately this would require changes in quite a few places: shared > descriptor, HW S/G generation logic, IV dma (un)mapping and maybe others. > > So it's better to have this fix now (which, considering size, is > appropriate for -stable) and later, if needed, offload IV updating in HW. > My apologies for reviving this thread from the dead, but doesn't the patch fail for in-place decryption since we are copying from req->dst after the operation is done, and therefore it no longer contains the ciphertext? I'm asking since I ran into a similar issue in the ccree driver and thought to deploy a similar fix but could not convince myself why this works. Thanks! Gilad -- Gilad Ben-Yossef Chief Coffee Drinker "If you take a class in large-scale robotics, can you end up in a situation where the homework eats your dog?" -- Jean-Baptiste Queru