netdev - Re: [PATCH v3 net-next 3/4] tls: kernel TLS support

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Message-ID: <20170711202402.GA48524@gmail.com>
Date:   Tue, 11 Jul 2017 13:24:02 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Dave Watson <davejwatson@...com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Ilya Lesokhin <ilyal@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        Boris Pismenny <borisp@...lanox.com>,
        Liran Liss <liranl@...lanox.com>,
        Matan Barak <matanb@...lanox.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Tom Herbert <tom@...bertland.com>, herbert@...dor.apana.org.au,
        linux-crypto@...r.kernel.org,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        nmav@...tls.org, fridolin.pokorny@...il.com
Subject: Re: [PATCH v3 net-next 3/4] tls: kernel TLS support

On Tue, Jul 11, 2017 at 11:53:11AM -0700, Dave Watson wrote:
> On 07/11/17 08:29 AM, Steffen Klassert wrote:
> > Sorry for replying to old mail...
> > > +int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx)
> > > +{
> > 
> > ...
> > 
> > > +
> > > +	if (!sw_ctx->aead_send) {
> > > +		sw_ctx->aead_send = crypto_alloc_aead("gcm(aes)", 0, 0);
> > > +		if (IS_ERR(sw_ctx->aead_send)) {
> > > +			rc = PTR_ERR(sw_ctx->aead_send);
> > > +			sw_ctx->aead_send = NULL;
> > > +			goto free_rec_seq;
> > > +		}
> > > +	}
> > > +
> > 
> > When I look on how you allocate the aead transformation, it seems
> > that you should either register an asynchronous callback with
> > aead_request_set_callback(), or request for a synchronous algorithm.
> > 
> > Otherwise you will crash on an asynchronous crypto return, no?
> 
> The intention is for it to be synchronous, and gather directly from
> userspace buffers.  It looks like calling
> crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC) is the correct way
> to request synchronous algorithms only?
> 

Yes, that means the CRYPTO_ALG_ASYNC bit is required to be 0, i.e. the algorithm
must be synchronous.  Currently it's requesting either a synchronous or
asynchronous algorithm, and it will crash if it gets an async one.

Also I think even with a synchronous algorithm, tls_do_encryption() still needs
to call aead_request_set_callback(), passing NULL for the callback and data, so
that the request flags are initialized.

Eric