linux-kernel - Re: Need help with failling gcm_base(ctr,ghash-generic) selftest

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Date:   Fri, 2 Aug 2019 07:18:30 +0200
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Pascal Van Leeuwen <pvanleeuwen@...imatrix.com>
Cc:     "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Need help with failling gcm_base(ctr,ghash-generic) selftest

On Fri, Aug 02, 2019 at 12:24:04AM +0000, Pascal Van Leeuwen wrote:
> > -----Original Message-----
> > From: linux-crypto-owner@...r.kernel.org <linux-crypto-owner@...r.kernel.org> On Behalf Of
> > Corentin Labbe
> > Sent: Thursday, August 1, 2019 9:43 PM
> > To: herbert@...dor.apana.org.au; linux-crypto@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Subject: Need help with failling gcm_base(ctr,ghash-generic) selftest
> > 
> > Hello
> > 
> > I am writing the Allwinner sun8i-ce driver and when running tcrypt I got
> > [   30.201739] alg: aead: gcm_base(ctr-aes-sun8i-ce,ghash-generic) decryption failed on test
> > vector 3; expected_error=0, actual_error=-74, cfg=\"random: may_sleep use_digest
> > src_divs=[100.0%@...14] dst_divs=[5.90%@...gnmask+3015, 60.56%@...96, 17.92%@...5,
> > 15.62%@+10]\"
> > or
> >
> The decryption reports only an -EBADMSG here, which means the decryption itself went
> fine, but the authentication tag mismatched.
> 
> 
> > [  148.613537] alg: aead: gcm_base(ctr-aes-sun8i-ce,ghash-generic) encryption test failed
> > (wrong result) on test vector 2, cfg=\"random: may_sleep use_final src_divs=[100.0%@+0]
> > iv_offset=20\"
> > 
> Can't say for sure, but considering the decrypt error, this is most likely just a
> mismatch on the appended authentication tag.
> 
> > Since ctr-aes-sun8i-ce is passing the ctr(aes) selftest, I dont understand what could be
> > wrong.
> > 
> That is possible, as this appears to be a problem with the authentication part,
> not the encryption part. So possibly a problem with the way you setup the 
> authentication key (which is actually derived from the encryption key, but I don't
> know if your hardware does this autonomously, mine doesn't) and/or operation?
> 

But since my driver is just a skcipher, I dont understand why I should care about any aead part, right ?