linux-kernel - Re: crypto: user - crypto_alg

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Message-ID: <20141125084225.GY6390@secunet.com>
Date:	Tue, 25 Nov 2014 09:42:25 +0100
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Stephan Mueller <smueller@...onox.de>
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: crypto: user - crypto_alg_match removal

On Mon, Nov 24, 2014 at 01:29:10PM +0100, Stephan Mueller wrote:
> Am Montag, 24. November 2014, 08:22:46 schrieb Steffen Klassert:
> 
> > With crypto_alg_lookup() we don't know whether the match is based on
> > the driver or the algorithm name. That's why we have crypto_alg_match(),
> > here we can ask for a driver or an algorithm match. In some situations it
> > is important to have an exact match on the crypto driver name. For example
> > if a user wants to instantiate or delete a certain inplementation of an
> > algorithm. In this case we need to know whether this exact algorithm
> > driver is registered in the system.
> 
> I understand. But going with the logic of the kernel crypto API, if one needs 
> an exact match, you pick the driver name. Otherwise the generic name. 
> crypto_alg_lookup returns the exact algo when you supply a driver name. It 
> returns the algo with the highest prio when you supply a generic name.
> 
> I do not see a difference for the scenarios you describe.

Well, I think there is a small but important difference. If a user
requests a driver name that would match an algorithm name (i.e. cbc(aes)
instead of cbc(aes-asm)) crypto_alg_lookup() returns the algorithm with
the highest priority instead of telling that we don't have a driver with
the name cbc(aes).

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