linux-kernel - Re: [PATCH 0/5] Add KDF implementations to crypto API

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Message-ID: <X/axTBTMGpJ07tft@sol.localdomain>
Date:   Wed, 6 Jan 2021 22:59:24 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Stephan Mueller <smueller@...onox.de>
Cc:     herbert@...dor.apana.org.au, mathew.j.martineau@...ux.intel.com,
        dhowells@...hat.com, linux-crypto@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH 0/5] Add KDF implementations to crypto API

On Thu, Jan 07, 2021 at 07:37:05AM +0100, Stephan Mueller wrote:
> Am Montag, dem 04.01.2021 um 14:20 -0800 schrieb Eric Biggers:
> > On Mon, Jan 04, 2021 at 10:45:57PM +0100, Stephan Müller wrote:
> > > The HKDF addition is used to replace the implementation in the filesystem
> > > crypto extension. This code was tested by using an EXT4 encrypted file
> > > system that was created and contains files written to by the current
> > > implementation. Using the new implementation a successful read of the
> > > existing files was possible and new files / directories were created
> > > and read successfully. These newly added file system objects could be
> > > successfully read using the current code. Yet if there is a test suite
> > > to validate whether the invokcation of the HKDF calculates the same
> > > result as the existing implementation, I would be happy to validate
> > > the implementation accordingly.
> > 
> > See https://www.kernel.org/doc/html/latest/filesystems/fscrypt.html#tests
> > for how to run the fscrypt tests.  'kvm-xfstests -c ext4 generic/582' should
> > be
> > enough for this, though you could run all the tests if you want.
> 
> I ran the $(kvm-xfstests -c encrypt -g auto) on 5.11-rc2 with and without my
> HKDF changes. I.e. the testing shows the same results for both kernels which
> seems to imply that my HKDF changes do not change the behavior.
> 
> I get the following errors in both occasions - let me know if I should dig a
> bit more.

The command you ran runs almost all xfstests with the test_dummy_encryption
mount option enabled, which is different from running the encryption tests --
and in fact it skips the real encryption tests, so it doesn't test the
correctness of HKDF at all.  It looks like you saw some unrelated test failures.
Sorry if I wasn't clear -- by "all tests" I meant all encryption tests, i.e.
'kvm-xfstests -c ext4 -g encrypt'.  Also, even the single test generic/582
should be sufficient to test HKDF, as I mentioned.

- Eric