On Fri, 7 Jun 2019 at 22:24, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote: > > Hi Eric, > > >> One of the issues that I would like to see addressed in the crypto API > >> is they way the cipher abstraction is used. In general, a cipher should > >> never be used directly, and so it would be much better to clean up the > >> existing uses of ciphers outside of the crypto subsystem itself, so that > >> we can make the cipher abstraction part of the internal API, only to > >> be used by templates or crypto drivers that require them as a callback. > >> > >> As a first step, this series moves all users of the 'arc4' cipher to > >> the ecb(arc4) skcipher, which happens to be implemented by the same > >> driver, and is already a stream cipher, given that ARC4_BLOCK_SIZE > >> actually evaluates to 1. > >> > >> Next step would be to switch the users of the 'des' and 'aes' ciphers > >> to other interfaces that are more appropriate, either ecb(...) or a > >> library interface, which may be more appropriate in some cases. In any > >> case, the end result should be that ciphers are no longer used outside > >> of crypto/ and drivers/crypto/ > >> > >> This series is presented as an RFC, since I am mostly interested in > >> discussing the above, but I prefer to do so in the context of actual > >> patches rather than an abstract discussion. > >> > >> Ard Biesheuvel (3): > >> net/mac80211: switch to skcipher interface for arc4 > >> lib80211/tkip: switch to skcipher interface for arc4 > >> lib80211/wep: switch to skcipher interface for arc4 > >> > > > > The way the crypto API exposes ARC4 is definitely broken. It treats it as a > > block cipher (with a block size of 1 byte...), when it's actually a stream > > cipher. Also, it violates the API by modifying the key during each encryption. > > > > Since ARC4 is fast in software and is "legacy" crypto that people shouldn't be > > using, and the users call it on virtual addresses, perhaps we should instead > > remove it from the crypto API and provide a library function arc4_crypt()? We'd > > lose support for ARC4 in three hardware drivers, but are there real users who > > really are using ARC4 and need those to get acceptable performance? Note that > > they aren't being used in the cases where the 'cipher' API is currently being > > used, so it would only be the current 'skcipher' users that might matter. > > > > Someone could theoretically be using "ecb(arc4)" via AF_ALG or dm-crypt, but it > > seems unlikely… > > that is not unlikely, we use ecb(arc4) via AF_ALG in iwd. It is what the WiFi standard defines to be used. > Ah ok, good to know. That does imply that the driver is not entirely broken, which is good news I suppose.
