> On Thu, 30 May 2019 at 15:58, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > wrote: > > > > On Thu, May 30, 2019 at 01:45:47PM +0000, Iuliana Prodan wrote: > > > > > > On the current structure of caamalg, to work, iv needs to be copied > > > before memcpy(iv, req->iv, ivsize), from skcipher_edesc_alloc > function. > > > For this we need edesc, but this cannot be allocated before knowing > how > > > much memory we need. So, to make it work, we'll need to modify more in > CAAM. > > > > All the copying does is: > > > > if (ivsize) > > scatterwalk_map_and_copy(req->iv, req->src, req- > >cryptlen - > > ivsize, ivsize, 0); > > > > Why do you need to allocate the edesc before doing this? > > > > Because that is where the incoming iv is currently consumed. Copying > it out like this wipes the input IV from memory. I had a similar problem for the Inside Secure driver: for decrypt operations, you need to copy the output IV from your input data buffer (it's the last input data cipher block) but you need to do that *before* you start the hardware, as for in-place operations, it is overwritten. At the same time, you cannot store it to req->iv yet, because that still contains the input IV that you need for processing the first block. The only solution I could come up with, is to park it in some temporary buffer in the skcipher_request_ctx *before* starting the hardware and copy it to req->iv *after* the operation completes. Regards, Pascal van Leeuwen Silicon IP Architect, Multi-Protocol Engines @ Inside Secure www.insidesecure.com
