Re: [Gen-art] Gen-art Telechat review of draft-ietf-nfsv4-rpcsec-gssv3-15

[Martin Stiemerling <[e-mail]>]

Hi Andy,

The telechat is happening today (01/21) at 4pm CET.

However, my understanding from the email thread with Nico is that there 
is a solutiong that needs to be folded into the draft, isnt't it?

In this case, there is no need to join the telechat.

Thanks,

   Martin


Am 20.01.16 um 20:49 schrieb Adamson, Andy:
>
>> On Jan 16, 2016, at 1:15 PM, Elwyn Davies <[e-mail]> wrote:
>>
>> I am the assigned Gen-ART reviewer for this draft. The General Area
>> Review Team (Gen-ART) reviews all IETF documents being processed
>> by the IESG for the IETF Chair. Please wait for direction from your
>> document shepherd or AD before posting a new version of the draft.
>>
>> For more information, please see the FAQ at
>>
>> <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
>>
>> Document: draft-ietf-nfsv4-rpcsec-gssv3-15.txt
>> Reviewer: Elwyn Davies
>> Review Date: 2016/01/16
>> IETF LC End Date: 2015/12/09
>> IESG Telechat date: 2016/01/21
>
> Hi Elwyn
>
> Where can I find the telechat details (time off call and phone #)?
>
>
>>
>> Summary: Almost ready.  Thank you for addressing my comments from the last call review.  For the record there are a couple of other points that have been raised elsewhere that need to be addressed.
>>
>> Major issues:
>> s2.7.1/s4: There is a security issue with RPCSEC_GSS_CREATE when multi-principal authentication is required.  See mail [1] below. This may have a (minor) knock-on effect of the NFSv4.2 specification where this is used; as currently specified (draft-ietf-nfsv4-minorversion2-40) use of privacy is already mandated for at least some of the relevant uses of RPCSEC_GSS_CREATE in NFSv4.2 which will mitigate the problem.  I have raised this issue in the Telechat review of the NFSv4.2 draft to ensure that privacy is mandated in *all* relevant cases - and to ensure changes are coordinated.
>
> NFSv4.2 does not use the multi-principal assertion.
>
> —>Andy
>
>>
>> Minor issues:
>> s2.7.1.4: Some refinement of the constraints on the rp_name string marked as 'human readable' would be desirable.
>>
>> Nits/editorial comments:
>> None
>>
>> ========================================
>> [1]
>>> From: Nico Williams <[e-mail]>
>>> Subject: Re: rpcsec-gssv3
>>> Date: January 11, 2016 at 8:01:52 PM EST
>>> To: Benjamin Kaduk <[e-mail]>
>>> Cc: Stephen Farrell <[e-mail]>, "[e-mail]" <[e-mail]>, Spencer Dawkins <[e-mail]>, Martin Stiemerling <[e-mail]>, "Adamson, Andy" <[e-mail]>
>>>
>>> On Thu, Jan 07, 2016 at 02:14:01PM -0600, Nico Williams wrote:
>>>> Ok, thanks.  I'll post a write up this Saturday.
>>>
>>> Or on Monday.
>>>
>>> OK, so, a while back Ben Kaduk noticed that there is a security problem
>>> with the RPCSEC_GSS_CREATE procedure with multi-principal
>>> authentication.
>>>
>>> The attack varies from easy to difficult to mount depending on whether
>>> the server implements a global or per-connection GSS context handle
>>> namespace, and whether it assigns them in a way that the attacker can
>>> get a specific context handle number assigned to it.
>>>
>>> There are two fixes, the simplest of which is to require that the
>>> RPCSEC_GSS_CREATE procedure be called with privacy protection when using
>>> the multi-principal authentication feature.
>>>
>>> To recap how the RPCSEC_GSS_CREATE procedure with multi-principal
>>> authentication feature works, the client first makes a MIC token with a
>>> GSS context that authenticates the user to the server, then it it uses
>>> that MIC in the payload of the RPCSEC_GSS_CREATE procedure. The
>>> RPCSEC_GSS_CREATE procedure is itself protected with a GSS context that
>>> authenticates the client.
>>>
>>> The problem is that the data that the user GSS context MICs is
>>> insufficiently strong a statement of intent because it only identifies
>>> the client host GSS context by its RPCSEC_GSS context handle ID and
>>> nothing more.  An attacker that can intercept an RPCSEC_GSS_CREATE
>>> procedure and cause the RPCSEC_GSS context handle to get re-assigned
>>> will be able to steal the victim's identity.
>>>
>>> There are a number of solid fixes that fall into two classes:
>>>
>>> 1) Add to the data that the user context MICs in order to improve the
>>>    quality of the statement of intent.
>>>
>>>    E.g., add the client host principal's name.  Or add a MIC made with
>>>    the client host's GSS context.
>>>
>>> 2) Make it so the attacker cannot steal the MIC made with the user GSS
>>>    context.
>>>
>>>    E.g., use privacy protection for the RPCSEC_GSS_CREATE procedure,
>>>    thus the MIC made with the user GSS context cannot be obtained by the
>>>    attacker without having the client host's or server's credentials.
>>>    Stephen proposed this.
>>>
>>>    (The OpenAFS rxgk protocol uses GSS_Pseudo_random() [RFC4401] to
>>>    similar effect.)
>>>
>>> At this stage the simplest thing to do is to require that clients always
>>> use privacy protection for the RPCSEC_GSS_CREATE procedure. Note
>>> that there is nothing that the server can do to prevent this attack if
>>> clients don't use privacy protection for this, but the server should
>>> still reject RPCSEC_GSS_CREATE procedure calls without privacy
>>> protection.  (All of this is only for the multi-principal authentication
>>> case.)
>>>
>>> Nico
>>> --
>>
>>
>