Re: [secdir] Secdir review of draft-josefsson-kerberos5-starttls-08

[Simon Josefsson <[e-mail]>]

Thanks Magnus, I like your new text.  It appears to me like a
non-technical change, so I'll apply this change to my local copy.  I'll
wait until after the IESG evaluation to submit a new version though,
unless someone feels this should be done sooner for some reason?

/Simon

Magnus Nyström <[e-mail]> writes:

> This is a follow-up to the review I made back in December on version
> -07 of this document.
>
> Simon has implemented all the changes I proposed (and more!) and I
> have only one comment on this version, pertaining to the new text in
> Section 5. I cannot judge the validity of the statement that "Many
> client environments [presumably the ones that this protocol targets]
> do not have secure long-term storage, which is required to validate
> certificates", but assuming this statement is true, then, for clarity,
> I would suggest changing the 2nd and 3rd paragraph of the section to:
>
> "
> A goal for the protocol described in this memo is that it should be as
> easy to implement and deploy on clients as support for UDP/TCP. Since
> many client environments do not have secure long-term storage (and
> server certificate validation requires some form of long-term
> storage), the Kerberos V5 STARTTLS protocol does not require clients
> to verify server certificates. If server certification had been
> required, then environments with constrained clients such as those
> mentioned would be forced to disable TLS; this would arguably be worse
> than TLS without server certificate validation as use of TLS, even
> without server certificate validation, protects against some attacks
> that Kerberos V5 over UDP/TCP do not. For example, even without server
> certificate validation, TLS does protect against passive network
> sniffing aimed at tracking Kerberos service usage by a given client.
>
> Note however that use of TLS without server certificate verification
> opens up for a range of active attacks such as man-in-the-middle.
> "
>
> Best,
> -- Magnus