Re: [dhcwg] WGLC for draft-ietf-dhc-sedhcpv6-02 - Respond by May 18

[神明達哉 <[e-mail]>]

At Tue, 6 May 2014 07:36:34 +0000,
Sheng Jiang <[e-mail]> wrote:

> >- In Section 6.2:
> >
> >   On the recipient that supports the leap of faith model, the number of
> >   cached public keys or unverifiable certificates MUST be limited in
> >   order to protect against resource exhaustion attacks.  If the
> >
> >  This is mainly concerned about servers, correct?  If so, I'm not
> >  sure how severe this "attacks" are; DHCP servers generally need to
> >  maintain some state for each client (unless that's stateless only
> >  server) and would naturally already have some limitation on that
> >  resource.  Shouldn't the general defense be enough for this
> >  particular resource, too?
>
> The "MUST" here seems not proper. Let us replace is with "MAY". It makes this point optional and should address your concern.

I don't think my main point is MUST vs MAY.  It's about a more
general point of authenticating messages from clients to servers:

- whether we really need (public key) authentication in that
  direction, and if we do, why

- also if we do, what's the commonly expected model of "trust anchor":
  leap of faith or use of CA or something else, and if it's more
  likely to be a weaker model like leap of faith (I suspect so, for
  the direction of clients to servers), whether the motivation (1st
  bullet) is worth the weaker security

- and, if it's more likely to rely on leap of faith, what kind of
  consideration is needed

The discussion on caching the public keys is just a part of the third
bullet.  What I'm missing in the current draft is more comprehensive
and higher level discussions on all of these points.  It's far from
obvious to me compared to authenticating messages from servers to
clients.

--
JINMEI, Tatuya