Re: [nfsv4] Thinking about an RFC5661bis.

[David Noveck <[e-mail]>]

>>     It may be that we will need to explicitly discourage use
>> of AUTH_SYS  in an rfc5661bis (without, I hope, going so far as "SHOULD
>> NOT").

> It will be interesting to see what the text around that looks like --
> starting from just the Internet threat model of RFC 3552

I think I'll have to look at that document intensely.  Thanks for pointing
me to it.

> it's hard for me
> to imagine that behavior like AUTH_SYS would be anything other than
"SHOULD
> NOT".

You're right it does seem hard to imagine.  However, in this case
imagination
is not required.  You just have to look at what happened:

   - On 9/19/2008, this working group requested publication of
   draft-ietf-nfsv4-minorversion1-26.txt which presented use of AUTH_SYS as
   optional/allowed.
   - On 12/19/2008, the IESG approved publication of
   draft-ietf-nfsv4minorversion1-29.txt as a Proposed Standard, even though
   that document still  presented use of AUTH_SYS as optional/allowed.
   - On 1/14/2010, RFC5661 was published as a Proposed Standard with the
   treatment of AUTH_SYS intact.
   - Since then, implementations have been developed and deployed which
   used AUTH_SYS, including many deployments in environments in which use of
   AUTH_SYS could reasonably be felt to be imprudent, leading to a troubling
   security situation for NFSv4.1.

People may well have different views as to how to assign the
responsibility/blame for this situation and there is no real point in
trying to  do so.  Clearly, the authors, the other members of the working
group, and the IESG all had some role.

The descision not to say "SHOULD NOT" with regard to NFSv4.1 has already
been made and I don't see how it can be changed even one thinks that the
working roup was wrong to write RFC5661 that way or that the IESG was wrong
to approve publication.   A Security Considerations section can still draw
attention to the problems that use of AUTH_SYS can give rise to, and the
steps necessary to mitigate them, where possible.

> But please to not take this as trying to discourage you from trying,
> and rather as a chance to educate the security folk.

I'm not sure what education I can provide.   I'm sure people will want to
know how this happened but all I can provide are guesses.   I think I can
learn stuff about security from the exercise.

>>I think we need to frame the discussion around the three big
>> security deficits present using AUTH_SYS in the clear (exposing your data
>> to prying eves, using  data that has traversed the newtwork without
>> integrity protection, acting on unauthenticated requests) and not on the
>> use of AUTH_SYS per se.  If we do this, we can publish and implement

> Dividing things into risks and countermeasures is usually a good strategy,

Good point.

> rather than focusing specifically on mechanisms, yes...

We have had a number of situations in which some particular mechanism was
felt to be salvific, but turned out not to be so :-(

>> rpc-tls without needng to further deal with the security considerations
>> section of the NFSv4.1 spec.

> ...since once you start talking about *properties* of the protocol
> components, it's easier to slot different backends into place, provided
> that they provide the same (or better) properties.

True.  The conclusion I draw is that rpc-tls will have to be fairly far
along
in its development when the bis document is considered, even if it doesn't
have to be published first.    If it seems that equal (or better) security
is clearly
on the horizon, I think the security people will be OK with a treatment
that
does not stigmtize AUTH_SYS per se, but instead draws attention to the
exposure of data in transit, the lack of integrity protection, and the
execution
of unautheticated requests.

Given the need for rpc-tls to be fairly far along, the delays that Tom is
worried
about do not seem to be all that troubling, since there is really no rush
to get
5661bis out, even if we think it is needed/desirable.

On Thu, Feb 28, 2019 at 8:00 PM Benjamin Kaduk <[e-mail]> wrote:

> On Thu, Feb 28, 2019 at 09:37:28AM -0500, David Noveck wrote:
> > A number of review comments regarding draft-ietf-nfsv4-mv1-msns-update
> have
> > raised the issue of a possible bis document for NFSv4.1.   These range
> all
> > the way from those assuming that mv1-msns-update is a stepping stone on
> the
> > way to the bis document, which I agree with, to those that are asking us
> to
> > explain why we haven't already done that.   I will have to respond to
> that
> > latter comment, but I'm hoping to delay that until after the telechat.
>
> Thanks for starting this thread.  Since I am reading already...
>
> > In any case, it seems that we have accumulated enough changes to and
> issues
> > with RFC5661 that we need to start thinking about producing a bis
> > document.  These include:
> >
> [...]
> >
> > The joker in this particular pack is the Security Considerations section.
> >  While we have to address the Security Directorate's notorious,
> "collection
> > of random observations" comment, I think we need to do so in a way that
> is
> > compatible with the expected draft-nfsv4-rpc-tls (hint, hint), even
> though
> > we want to be able to publish without waiting for rpc-tls to become an
> > RFC.  While draft-cel-rpc-tls-02 states that use of AUTH_SYS is currently
> > "discouraged" and that is a fair summary, I don't think RF5661 ever does
> > that explicitly.   It may be that we will need to explicitly discourage
> use
> > of AUTH_SYS  in an rfc5661bis (without, I hope, going so far as "SHOULD
> > NOT").  I think we need to frame the discussion around the three big
>
> It will be interesting to see what the text around that looks like --
> starting from just the Internet threat model of RFC 3552 it's hard for me
> to imagine that behavior like AUTH_SYS would be anything other than "SHOULD
> NOT".  But please to not take this as trying to discourage you from trying,
> and rather as a chance to educate the security folk.
>
> > security deficits present using AUTH_SYS in the clear (exposing your data
> > to prying eves, using  data that has traversed the newtwork without
> > integrity protection, acting on unauthenticated requests) and not on the
> > use of AUTH_SYS per se.  If we do this, we can publish and implement
>
> Dividing things into risks and countermeasures is usually a good strategy,
> rather than focusing specifically on mechanisms, yes...
>
> > rpc-tls without needng to further deal with the security considerations
> > section of the NFSv4.1 spec.
>
> ...since once you start talking about *properties* of the protocol
> components, it's easier to slot different backends into place, provided
> that they provide the same (or better) properties.
>
> -Ben
>