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From: Eric Biggers <ebiggers@kernel.org>
To: Thara Gopinath <thara.gopinath@linaro.org>
Cc: herbert@gondor.apana.org.au, davem@davemloft.net,
	bjorn.andersson@linaro.org, ardb@kernel.org,
	sivaprak@codeaurora.org, linux-crypto@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 05/11] crypto: qce: skcipher: Return error for zero length messages
Date: Thu, 4 Feb 2021 16:26:13 -0800	[thread overview]
Message-ID: <YByQpRG0SC0k0gYC@gmail.com> (raw)
In-Reply-To: <00d759f3-8ea3-1f85-b623-225c372c0a04@linaro.org>

On Thu, Feb 04, 2021 at 07:09:53PM -0500, Thara Gopinath wrote:
> > > @@ -260,6 +261,10 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
> > >   	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
> > >   	keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
> > > +	/* CE does not handle 0 length messages */
> > > +	if (!req->cryptlen)
> > > +		return -EOPNOTSUPP;
> > > +
> > 
> > For the algorithms in question, the correct behavior is to return 0.
> 
> What do you mean? The driver should return a 0 ?

Yes, there is nothing to do for empty inputs, so just return 0 (success).

> > Aren't the tests catching that difference?
> 
> I was anyways planning on sending an email to the list with these queries.
> But since you asked,  these are my observations with fuzz testing which I
> have been doing quite a bit now (I am also working on adding a few qualcomm
> AEAD algorithms support in mainline).
> 
> - if the generic algorithm supports 0 length messages and the transformation
> I am testing does not, the test framework throws an error and stops.
> - key support mismatch between the generic algorithm vs my algorithm /engine
> also does the same thing.For eg, Qualcomm CE engine does not support any
> three keys being same for triple des algorithms. Where as a two key 3des is
> a valid scenario for generic algorithm(k1=k3). Another example is hardware
> engine not supporting AES192.
> 
> How are these scenarios usually handled ? Why not allow the test framework
> to proceed with the testing if the algorithm does not support a particular
> scenario ?

Omitting support for certain inputs isn't allowed.  Anyone in the kernel who
wants to use a particular algorithm could get this driver for it, and if they
happen to use inputs which the driver decided not to support, things will break.

The way that drivers handle this is to use a fallback cipher for inputs they
don't support.

- Eric

  reply	other threads:[~2021-02-05  0:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-04 21:43 [PATCH v5 00/11] Regression fixes/clean ups in the Qualcomm crypto engine driver Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 01/11] crypto: qce: sha: Restore/save ahash state with custom struct in export/import Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 02/11] crypto: qce: sha: Hold back a block of data to be transferred as part of final Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 03/11] crypto: qce: skcipher: Return unsupported if key1 and key 2 are same for AES XTS algorithm Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 04/11] crypto: qce: skcipher: Return unsupported if any three keys are same for DES3 algorithms Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 05/11] crypto: qce: skcipher: Return error for zero length messages Thara Gopinath
2021-02-04 22:48   ` Eric Biggers
2021-02-05  0:09     ` Thara Gopinath
2021-02-05  0:26       ` Eric Biggers [this message]
2021-02-05 14:08         ` Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 06/11] crypto: qce: skcipher: Return error for non-blocksize data(ECB/CBC algorithms) Thara Gopinath
2021-02-04 22:50   ` Eric Biggers
2021-02-05  0:24     ` Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 07/11] crypto: qce: skcipher: Set ivsize to 0 for ecb(aes) Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 08/11] crypto: qce: skcipher: Improve the conditions for requesting AES fallback cipher Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 09/11] crypto: qce: common: Set data unit size to message length for AES XTS transformation Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 10/11] crypto: qce: Remover src_tbl from qce_cipher_reqctx Thara Gopinath
2021-02-04 21:43 ` [PATCH v5 11/11] crypto: qce: Remove totallen and offset in qce_start Thara Gopinath

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