Subject: RE: Error in ips-security-07

From: [email-masked]
Date: Sat, 26 Jan 2002 03:31:32 -0500

This is the infamous "dangling SA" issue discussed in ipsec
in the past.  While I don't recall its resolution, the IKEv2
draft prohibits dangling SAs, and the IPS Security draft is
taking the same position.  OTOH, I seem to recall that IKEv1
implementations differ on whether dangling SAs are allowed.
Paul - are you suggesting that prohibiting dangling SAs
would unnecessarily exclude some IKEv1 implementations to
our detriment?

Thanks,
--David  
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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
+1 (508) 249-6449 *NEW*      FAX: +1 (508) 497-8500
[email-masked]         Cell: +1 (978) 394-7754
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> -----Original Message-----
> From: Paul Koning [mailto:[email-masked]]
> Sent: Wednesday, January 23, 2002 7:10 PM
> To: [email-masked]; [email-masked]
> Subject: RE: Error in ips-security-07
> 
> 
> Excerpt of message (sent 23 January 2002) by KRUEGER,MARJORIE 
> (HP-Roseville,ex1):
> > Was this a typo?:
> >  
> > > The text in the security draft is based on a mistaken 
> assumption.  In
> > > fact, sessions are not bound to Phase 2 SAs in the first 
> place -- only
> > > to Phase 2 SAs. 
> >       ^^^^^^^
> > Did you mean Phase 1 SAs?  Otherwise this sentence doesn't 
> make sense?
> 
> Oops, yes, that's a typo, but not that way around.  Here's what I
> meant:
> 
>   The text in the security draft is based on a mistaken assumption.
>   In fact, sessions are not bound to Phase 1 SAs in the first place --
>   only to Phase 2 SAs.
> 
>         paul
>

---

From: Paul Koning <[email-masked]>
Date: Mon, 28 Jan 2002 10:35:33 -0500

> would unnecessarily exclude some IKEv1 implementations to

I'm not sure what "dangling SAs" are, or whether that term applies to
the case you're talking about here.  I'll have to look at IKEv2 to see
what the story is there.

As for IKEv1, the spec explicitly discusses deleting the Phase 1 SA
immediately after the Phase 2 negotation (Quick Mode) has been
performed, in situations where you want Perfect Forward Secrecy.   So
it's not just that this is silently permitted -- it is explicitly
recommended.  Therefore I think it is a very bad idea for the IPS
security spec to explicitly disallow that same behavior!

I've run into several implementations that built in an assumption that
the Phase 2 SA is subordinate to the Phase 1 SA.  That's simply a
wrong assumption, as the text I quoted makes clear, and such
assumptions caused interop problems in interop test sessions.  I
remember having to fix this bug in our implementation at some point.
We need to make sure we don't duplicate those bugs here.

In any event, I cannot see any reason for the IPS spec to discuss this
topic at all.  SAs should be deleted when the IKE/IPsec specs call for
their deletion and not otherwise.  Why should IPS care what those
rules are?  We already have a lot of dabbling in internal IPsec/IKE
detail going on in the IPS security spec.  Talking about requirements
subsetting is one thing -- restating IKE algorithms is quite another,
especially if the restatement conflicts with the authoritative text.

It *is* correct for the IPS spec to say what you do to a connection
when the SA protecting it goes away.  That's already covered (on page
12); the current text makes sense to me.

	paul