On Thu, 26 Sep 2019 at 16:03, Pascal Van Leeuwen <[email protected]> wrote: > > > -----Original Message----- > > From: Ard Biesheuvel <[email protected]> > > Sent: Thursday, September 26, 2019 3:16 PM > > To: Pascal Van Leeuwen <[email protected]> > > Cc: Jason A. Donenfeld <[email protected]>; Linux Crypto Mailing List <linux- > > [email protected]>; linux-arm-kernel > > <[email protected]>; > > Herbert Xu <[email protected]>; David Miller > > <[email protected]>; Greg KH > > <[email protected]>; Linus Torvalds > > <[email protected]>; Samuel > > Neves <[email protected]>; Dan Carpenter <[email protected]>; Arnd > > Bergmann > > <[email protected]>; Eric Biggers <[email protected]>; Andy Lutomirski > > <[email protected]>; > > Will Deacon <[email protected]>; Marc Zyngier <[email protected]>; Catalin > > Marinas > > <[email protected]> > > Subject: Re: [RFC PATCH 00/18] crypto: wireguard using the existing crypto > > API > > > > On Thu, 26 Sep 2019 at 15:06, Pascal Van Leeuwen > > <[email protected]> wrote: > > ... > > > > > > > > My preference would be to address this by permitting per-request keys > > > > in the AEAD layer. That way, we can instantiate the transform only > > > > once, and just invoke it with the appropriate key on the hot path (and > > > > avoid any per-keypair allocations) > > > > > > > This part I do not really understand. Why would you need to allocate a > > > new transform if you change the key? Why can't you just call setkey() > > > on the already allocated transform? > > > > > > > Because the single transform will be shared between all users running > > on different CPUs etc, and so the key should not be part of the TFM > > state but of the request state. > > > So you need a transform per user, such that each user can have his own > key. But you shouldn't need to reallocate it when the user changes his > key. I also don't see how the "different CPUs" is relevant here? I can > share a single key across multiple CPUs here just fine ... >
We need two transforms per connection, one for each direction. That is how I currently implemented it, and it seems to me that, if allocating/freeing those on the same path as where the keypair object itself is allocated is too costly, I wonder why allocating the keypair object itself is fine. But what I am suggesting is to use a single TFM which gets shared by all the connections, where the key for each operation is provided per-request. That TFM cannot have a key set, because each user may use a different key.
