netdev - Re: Does ESP support 64 bit sequence numbering for authentication hash ?

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Date:	Thu, 15 Jan 2009 16:56:44 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	djenkins@...sta.com
Cc:	linux-crypto@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: Does ESP support 64 bit sequence numbering for authentication
	hash ?

Dean Jenkins <djenkins@...sta.com> wrote:
> 
> Does ESP support 64 bit sequence numbering for use with the
> authentication HMAC ?

We don't support 64-bit sequence numbers yet.  If you look at
struct xfrm_replay_state which is where we store the sequence
number internally you'll find that it uses u32s.

Patches for 64-bit support are welcome of course.

> I've looked at struct aead_givcrypt_request and it has a u64 seq member.
> Does ESP populate this with a 64 bit sequence number ?

That's different.  That's a generic value used to construct the IV.

> If 32 bit sequence numbering negotiated then how does the HMAC routine
> know that it should not use the top 32 bits of seq ? Or is it simply
> that if the top 32 bits are zero then the HMAC just uses the lower 32
> bits ?

Because the value we start out with is a u32, the high bits are
never set for IPsec.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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