netdev - Re: [PATCH net v3 3/3] esp, ah: modernize the crypto algorithm selections

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Message-ID: <20200610155312.GB1339@sol.localdomain>
Date:   Wed, 10 Jun 2020 08:53:12 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Tobias Brunner <tobias@...ongswan.org>
Cc:     netdev@...r.kernel.org, linux-crypto@...r.kernel.org,
        Corentin Labbe <clabbe@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net v3 3/3] esp, ah: modernize the crypto algorithm
 selections

On Wed, Jun 10, 2020 at 11:03:55AM +0200, Tobias Brunner wrote:
> Hi Eric,
> 
> > +	  Note that RFC 8221 considers AH itself to be "NOT RECOMMENDED".  It is
> > +	  better to use ESP only, using an AEAD cipher such as AES-GCM.
> 
> What's NOT RECOMMENDED according to the RFC is the combination of ESP+AH
> (i.e. use ESP only for confidentiality and AH for authentication), not
> AH by itself (although the RFC keeps ENCR_NULL as a MUST because ESP
> with NULL encryption is generally preferred over AH due to NATs).
> 
> Regards,
> Tobias

Okay, I'll drop this paragraph.  I'm surprised that authentication-only is still
considered a valid use case though.

- Eric