Re: SAs that carry fragments Was: Re: Some IKEv2 issues

[Nicolas Williams <Nicolas.Williams@sun.com>]

On Fri, Feb 20, 2004 at 03:56:17PM -0600, Nicolas Williams wrote:
> I'd better read Charlie Lynn's proposal now :)

IIUC Charlie Lynn's proposal is to assign one SA to protect all
fragments even though multiple SAs may be used for different ports, yes?

I think this defeats the notion of having SGs with SPD entries with port
selectors where the different SAs for the same SA end-points have
effectively different IDs (e.g., different userFqdn IDs), though this
can be mitigated.  Presumably such cases involve a multi-user end-point
and this multi-user end-point runs trusted code (i.e., its OS kernel)
and may even have a host cert/key; using an SA whose ID corresponds to
the host for protecting the fragments would be a fine mitigation, as
would multiply-authenticating[*] the SA for carrying fragments (as long
as the trusted code in the end-point protects its DH private numbers and
SA keys from its users).

As compared to Tero's proposal (and with my comments) this is a lighter
weight solution -- setting up an SA and adding an SPD entry may be a
burden, but that would be less than the burden of keeping initial
fragment selector/ID cache (see previous post).

[*]  Is it possible to run multiple AUTH exchanges for a single IKE_SA
     with different certs?  Obviously the IKE_SA can only have one
     IDi/IDr...

Nico
--