Am Donnerstag, 13. Juli 2017, 20:10:57 CEST schrieb Eric Biggers: Hi Eric, > Hi Stephan, > > On Thu, Jul 13, 2017 at 04:54:55PM +0200, Stephan Müller wrote: > > Am Mittwoch, 12. Juli 2017, 23:00:32 CEST schrieb Eric Biggers: > > > > Hi Herbert, > > > > This patch adds a second KDF to the kernel -- the first is found in the > > keys subsystem. > > > > The next KDF that may come in is in the TLS scope. > > > > Would it make sense to warm up the KDF patches adding generic KDF support > > to the kernel crypto API that I supplied some time ago? The advantages > > would be to have one location of KDF implementations and the benefit of > > the testmgr. > That may be a good idea. Looking at the old thread, I share Herbert's > concern (http://www.spinics.net/lists/linux-crypto/msg21231.html) about > there likely not being more than one implementation of each KDF algorithm. > So, perhaps some simple helper functions would be more appropriate. > However, making the KDFs be covered by self-tests would be very nice. I agree that it is likely that specific KDF implementations may only be used once. But still, I would recommend to maintain those implementation under the crypto API umbrella, as KDFs are cryptographic operations. > > Also, it seems your patch > (http://www.spinics.net/lists/linux-crypto/msg21137.html) doesn't allow a > salt to be passed in. In order to fully support HKDF, crypto_rng_reset() > (which as I understand would be the way to invoke the "extract" step) would > somehow need to accept both the input keying material and salt, both of > which are arbitrary length binary. I concur with you. I have implemented the HKDF in my libkcapi as well and saw the need for a salt. Let me work on an update to the KDF patch for the kernel crypto API. Ciao Stephan
