linux-kernel - Re: [PATCH v2] crypto: algif_skcipher

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Date:	Sun, 3 Jan 2016 10:42:28 +0100
From:	Milan Broz <gmazyland@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Stephan Mueller <smueller@...onox.de>,
	Dmitry Vyukov <dvyukov@...gle.com>, syzkaller@...glegroups.com,
	davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, kcc@...gle.com, glider@...gle.com,
	edumazet@...gle.com, sasha.levin@...cle.com, keescook@...gle.com
Subject: Re: [PATCH v2] crypto: algif_skcipher - Require setkey before
 accept(2)

On 01/03/2016 02:31 AM, Herbert Xu wrote:
> On Sat, Jan 02, 2016 at 09:18:30PM +0100, Milan Broz wrote:
>>
>> But I cannot change thousands of cryptsetup installations that are actively using that code.
>> This is clear userspace breakage which should not happen this way.
> 
> I'll try to add some compatibility code for your case, assuming
> your modus operandi is accept(2) followed by a single setkey before
> proceeding to encryption/decryption.

Hi,

yes, basically it prepares socket()/bind()/accept() and then it calls setkey once.
(I'll try to fix in next releases to call setkey first though.)

I am doing exactly the same for AF_ALG HMAC (hmac(<hash>) key,
does this requirement for order if accept/setkey applies there as well?
(It is not enforced yet.)

Anyway, you can easily simulate that skcipher API call just with running "cryptsetup benchmark"
(with accept() patch it will print N/A for all ciphers while without patch it measures some
more-or-less magic performance numbers :)

> 
>> (Moreover it still doesn't work for cipher_null that has min/max key size 0.)
> 
> Setkey works just fine on cipher_null.

Yes, it works if ALG_SET_KEY is set to zero-length key.
I just re-introduced old bug to code, sorry.

Thanks!
Milan
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