From: Stephan =?ISO-8859-1?Q?M=FCller?= Subject: Re: [PATCH 3/6] fscrypt: use HKDF-SHA512 to derive the per-inode encryption keys Date: Fri, 14 Jul 2017 17:50:06 +0200 Message-ID: <6581107.6MsbyqD4B1@positron.chronox.de> References: <20170712210035.51534-1-ebiggers3@gmail.com> <2034167.Brpu2WxA6s@tauon.chronox.de> <20170713181057.GA143898@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: "Theodore Y . Ts'o" , herbert@gondor.apana.org.au, Eric Biggers , Alex Cope , linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org, linux-crypto@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-ext4@vger.kernel.org To: Eric Biggers Return-path: In-Reply-To: <20170713181057.GA143898@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net List-Id: linux-crypto.vger.kernel.org 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 M=FCller 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 suppo= rt > > 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 use= d = once. But still, I would recommend to maintain those implementation under t= he = 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) wou= ld > 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 s= aw = the need for a salt. Let me work on an update to the KDF patch for the kernel crypto API. Ciao Stephan ---------------------------------------------------------------------------= --- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot