eap Mailing List: Re: TLS clarifications (Re: Ordered delivery of EAP messages)

[Lakshminath Dondeti (ldondeti]

Yoshihiro Ohba wrote:
> Let's forget about DTLS and focus on TLS.  I was arguing that
> correctness and security are different things.

I understand this part.  But, I am not sure the example fits, but it 
doesn't matter.  I am glad to understand your position. :)  Thanks for 
explaining.

So, moving forward from here, let's consider a question along the lines 
Avi has been asking, (note: this may not exactly be the question he asked)

Do EAP methods require in-order delivery to support any of their 
security properties?

I think yes; for example, TTLS would need in-order delivery for
"Replay protection:        Yes"
in Section 9 of draft-funk-eap-ttls-v1-01.

Thoughts?

Lakshminath

> If TLS are used over unreliable transport, of course it is not
> possible for TLS to maintain implicit sequence number.  Without
> reliable transport implicit sequence number would not work if loss or
> out-of-order delivery of TLS records happens and *even if there is no
> attacker*.  That is why I think that reliable transport is needed for
> TLS to make implicit sequence number work *correctly* so that it is
> used for *security*.  Maybe we are talking about the same thing in
> different ways.
>
> Yoshihiro Ohba
>
> On Sat, Mar 10, 2007 at 09:08:42PM -0800, Lakshminath Dondeti wrote:
> > Yoshihiro Ohba wrote:
> > > On Sat, Mar 10, 2007 at 02:37:11AM -0800, Lakshminath Dondeti wrote:
> > > > TLS requires reliable transport for replay protection.  (I guess Bernard 
> > > > was trying to get at this in another context in this thread)
> > > TLS requires reliable transport for implicit sequence number to work
> > > for replay protection.  
> > Right, that's what I was getting at.
> >
> > > But this does not mean replay attack is
> > > possible if TLS is run over unreliable transport.
> > How is the sequence number maintained in that case?  Are you saying that 
> > we might use an explicit sequence number as in DTLS?  But, we are not 
> > discussing DTLS, are we?
> >
> > What am I missing?
> >
> > thanks,
> > Lakshminath
> >
> > PS: To Avi's question, I was thinking in case of PEAP and TTLS if the 
> > EAP layer cannot guarantee in-order reliable delivery, how else do the 
> > endpoints maintain sequence numbers?  If there is no other way, we can 
> > conclude that PEAP and TTLS require in-order reliable delivery for one 
> > of its security guarantees.
> >
> > > Yoshihiro Ohba