Subject: Re: [RFC] [PATCH 06/11] esp4: Add support for IPsec extended sequence numbers

From: Steffen Klassert <[email-masked]>
Date: Tue, 8 Mar 2011 08:04:46 +0100

Sorry for the huge delay...

On Thu, Dec 02, 2010 at 03:29:47PM +0800, Herbert Xu wrote:
> On Mon, Nov 22, 2010 at 11:30:14AM +0100, Steffen Klassert wrote:
> >
> > @@ -205,11 +228,18 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
> >  	skb_to_sgvec(skb, sg,
> >  		     esph->enc_data + crypto_aead_ivsize(aead) - skb->data,
> >  		     clen + alen);
> > -	sg_init_one(asg, esph, sizeof(*esph));
> > +
> > +	if ((x->props.flags & XFRM_STATE_ESN)) {
> > +		sg_init_table(asg, 2);
> > +		sg_set_buf(asg, esph, sizeof(*esph));
> > +		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
> > +		sg_set_buf(asg + 1, seqhi, seqhilen);
> > +	} else
> > +		sg_init_one(asg, esph, sizeof(*esph));
> 
> I think this is wrong for AEAD algorithms.  You want the sequence
> number in network byte order for them so the high bits need to be
> inserted into the middle of the ESP header.
> 

Yes, indeed.

> The other problem is that you're currently requiring the authencesn
> user to provide two SG entries which is fine for now.  However,
> since this might be exported to user-space in future, authenecesn
> shouldn't really rely on that, or at least it shouldn't BUG.
> 
> So one solution is to do it based on bytes in authencesn.  That is,
> your associated input should always be 12 bytes long, and then you
> simply construct a new SG list for your actual processing with the
> middle 4 bytes taken out.
> 
> For IPsec it could just provide an SG list with three entries,
> of 4 bytes each.

Ok, I've updated the patchset in this regard.

> 
> Of course for simplicity, you could require this to be the case in
> authencesn and return -EINVAL (not BUG :) if it's not the case.
> 

Doing BUG was a leftover from debugging the thing. On debugging it is 
sometimes better to pull the emergency brake as soon as something
unexpected happens. I replaced BUG with return -EINVAL now.

I'll resend the patchset for a second round of review.