Re: [nfsv4] Comments on draft-ietf-nfsv4-integrity-measurement-07

[David Noveck <[e-mail]>]

> Appraisal is done at the point when file content is about to be used.
> With NFS, most frequently that would be on an NFS client system. That
> does not mean the NFS client implementation itself does the appraisal.

Perhaps not but the fact is that if you want to have a client implementation
you need to know the formal so that appraisal can be done correctly.   The
fact that this is not within the Linucx Client as you would describe it is
to me
a distinction without a difference.

> Suppose an OS implementer wants to implement something that interoperates
> with Linux's IMA. It is up to that implementer to approach the Linux IMA
> community and get them to provide this information.

That is the problem that people are concerned about.   I think some people
want one now  and I can see their point although I don't have any need for
this
data.

> Does anyone have suggestions as to where the Linux IMA community should
> go to publish a standard describing the integrity metadata format?
> Maybe the Trusted Computing Group ? Somewhere else?

I have no suggestions in this regard but am sure that if the Linux IMA
community
were willing to do this it could find some place suitable.

> Would it make sense to make up our own integrity metadata format just
> for NFS?

No.

> Or, perhaps we leave this explicitly to storage vendors to enable
> them to innovate.

I don't see much much interest in that.

> As the generation and appraisal of this metadata occurs
> outside of the filesystem, it is possible to provide plug-ins that handle
> this.

But to interoperate successfully everybody's plug-in would have to
implement the
same format.   That's why a specification of that format is needed to
provide
interoperability.

> The discussion in the room during IETF 105 suggested there was interest
> enough to move this document forward to publication.

There was and there still is.

> I thought this
> whole issue had been resolved at that time, as the conversation finished
> with an understanding that this was opaque metadata

It did but apparently there were people not present who now feel that it
cannot
be treated as totally opaque and needs to be documented.

> the next step was WGLC.

I still think it should be.   However, during WGLC, objections  will
inevitably be offered to the lack of a specfication of the integrity
metadata fomat. While I don't need this and would prefer that
this go forward even without it, I don't feel that these objections
can simply be dismissed.

> Of the two options, IMO option 1 is the only sensible one because there
> is no citable specification of what goes in the metadata.

The alternative is to create one.   I don't understand why it is so
difficult
given that there is an implementation that can be examined to determine
the format.


On Mon, Oct 28, 2019 at 2:40 PM Chuck Lever <[e-mail]> wrote:

>
>
> > On Oct 28, 2019, at 12:36 PM, spencer shepler <[e-mail]>
> wrote:
> >
> >
> > Chuck,
> >
> > inline for comments.
> >
> > On Mon, Oct 28, 2019 at 8:00 AM Chuck Lever <[e-mail]>
> wrote:
> > Hi Spencer, thanks for taking time to review this document. Responses
> > to individual comments are below.
> >
> >
> > > On Oct 28, 2019, at 2:50 AM, spencer shepler <
> [e-mail]> wrote:
> > >
> > >
> > > Feedback and comments on the draft “Integrity Measurement for Network
> File System version 4” - draft-ietf-nfsv4-integrity-measurement-07.
> > >
> > >
> > > Note that these comments are personal contribution and do not reflect
> my position as working group co-chair.
> > >
> > > In short, I am opposed to moving this draft to last call in its
> current state.  Generally, the draft describes the Linux implementation of
> a feature that is to be extended via NFS.  However, the description
> provided is insufficient for interoperable implementations to be achieved.
> >
> > Issues about interoperation have already been raised and addressed
> > multiple times both on the mailing list and in presentations at IETF
> > meetings. The metadata stored in this attribute is opaque to the NFS
> > protocol and implementations, just like file data is opaque.
> >
> > The metadata is not created by the NFS implementation; it is created
> > by a user space tool. It is not interpreted by the NFS implementation;
> > it is interpreted by a separate privileged security module.
> >
> > NetApp, for instance, could create a fully interoperating implementation
> > today, based solely on this document, simply by enabling clients to store
> > and retrieve this attribute. There is no more to it than that.
> >
> > NFS, in this case, is used as a transport. It is an intermediary. There's
> > no reason it needs to interpret the metadata. It's only job is to ensure
> > that data and metadata is not maliciously or accidentally altered.
> >
> > If the attribute is truly opaque to one implementation, then state it
> clearly.
>
> I don't understand the "if" clause. The NFS implementations do not
> interpret this metadata _ever_.
>
> The metadata can be interpreted on a server host by a private security
> module. But that is separate from the NFS server implementation itself.
> The NFS implementation on the server does not interpret this metadata.
> I'm defining a transport for the metadata, and nothing more.
>
>
> > If this is an attribute that is in support of the Linux method of
> operation and only ever intended to be such, then retitle the document to
> make that clear and remove the extraneous content of the document. This
> will make it clear to the reviewer what the intent is.
>
> How about "Transport and Storage of Linux Integrity Metadata for
> Network File System 4" ?
>
>
> > To the statement of the server implementation, the document refers to
> the server's ability to check the file content.  This to me meant that
> there was a client / server interoperability issue at hand.  I note that
> the server is not required to implement the capability but if it is
> possible, then it should be well defined.
>
> An NFS server is merely a vessel for integrity metadata. If the
> server happens to have an integrity appraisal module, then that
> module will process the metadata. The NFS server implementation
> itself does not parse this metadata.
>
>
> > > There are two options, in my opinion, to moving this document forward:
> > >
> > > 1)  Limit the description to the addition of the new, opaque attribute
> and corresponding errors that can be returned as a result of the
> interpretation of that attribute.
> > >
> > > 2)  Fully define the contents of the new attribute such that
> independent implementations can be achieved. This would include, but is not
> limited to, the open definition of the content of the new attribute and the
> procedures associated with defining new content and interpretation thereof.
> > >
> > > If option 1) were chosen, I would still be of the opinion that the
> draft should not move forward since it would present another barrier to
> open, interoperable implementations.
> >
> > "To move this document forward, pick option 1 or 2. But if you pick
> option
> > 1, I will still object."
> >
> > That means there is really only one option in your opinion. I have
> repeatedly
> > stated why option 2 is not practical or necessary. The nfsv4 working
> group
> > and the IETF does not want to be the bearer of the IMA standard for
> Linux.
> >
> > Further, there is no need for it do so, because the metadata stored in
> this
> > attribute is opaque to the NFS protocol and to NFS implementations.
> >
> > "Barrier to open implementations." The Linux implementation is open
> source.
> > It would certainly be possible to port the Linux implementation, or with
> a
> > little more work, provide a clean-room implementation. In an era in which
> > open source dominates, "open" no longer means just that there is an open
> > standard. Maybe "open" is not what you actually meant here.
> >
> > This is the question of client interoperability.  If two separate client
> implementations to follow the "IMA standard for Linux", then there should
> be an open definition of what that standard is in my opinion.
>
> There is no open definition of this metadata other than the
> implementation in Linux and the wiki that describes how to use it.
> In other words, IMA is an application that uses NFS (or any other file
> system) to store its data.
>
>
> > And I do mean the ability to implement with clarity about how and what
> implications there are for any intellectual property that exists.
> >
> >
> > Seems to me that rejecting a protocol mechanism that enables the use of a
> > data format with an open source implementation but no published standard
> is
> > also a barrier to open implementations.
> >
> > I am asking for clarity.  Either the attribute is opaque and that is
> clear to everyone or there is enough information to create interoperable
> implementations as mentioned above.
>
> It is opaque, period. There is not enough information in this document
> to implement appraisal, and that's on purpose. The document is meant
> to define a transport mechanism only.
>
>
> > > Note that I am also doubtful of the use case being presented. Using
> NFS to directly store and supply application executables seems to be in
> rapid decline or has already fallen out of use.  Given the rise of
> virtualization and the hosting of virtual disks on NFS along with the rise
> of containers and distribution thereof, application distribution seems to
> be a thing of the past with respect to their store/retrieval from NFS
> mounts.
> >
> > Do you have evidence that this change is taking place? Sharing the same
> > application executable on NFS seems pretty common in Oracle deployments.
> >
> > Do you believe IMA is not also useful for the read-only virtual disk use
> > case?
> >
> > One reason that virtual disks are used is /because/ NFS does not support
> > things like xattrs, capabilities, and integrity metadata. Otherwise,
> > maintaining guest root filesystems on NFS would be a popular solution.
> >
> > How about protection of other types of read-mostly data like
> configuration
> > files?
> >
> >
> > > If the effort was more focused on more traditional data integrity from
> source to consumption, that would be a more interesting use case.
>
> That's exactly what this mechanism is supposed to achieve. The metadata
> is a signed hash of the file's content. It is not interpreted and should
> remain unaltered from the point the content is created to the point
> where it is used. There, an independent mechanism appraises the content
> and the metadata to see if any alteration has occurred since the hash
> was signed.
>
> Appraisal is done at the point when file content is about to be used.
> With NFS, most frequently that would be on an NFS client system. That
> does not mean the NFS client implementation itself does the appraisal.
>
> The focus here is on read-mostly data (software distribution) because of
> the high overhead of re-signing the file content hash in a secure fashion.
> The key material is stored in TCMs.
>
>
> Suppose an OS implementer wants to implement something that interoperates
> with Linux's IMA. It is up to that implementer to approach the Linux IMA
> community and get them to provide this information.
>
> Does anyone have suggestions as to where the Linux IMA community should
> go to publish a standard describing the integrity metadata format?
> Maybe the Trusted Computing Group ? Somewhere else?
>
> Would it make sense to make up our own integrity metadata format just
> for NFS? Or, perhaps we leave this explicitly to storage vendors to enable
> them to innovate. As the generation and appraisal of this metadata occurs
> outside of the filesystem, it is possible to provide plug-ins that handle
> this.
>
>
> > With the rise of large scale data center usage of NFS (e.g. cloud
> computing) where customers expect data integrity or the identification of
> failure, the scale of cloud computing presents many opportunities for the
> loss of data integrity and NFS (and the client and server implementations
> thereof) do nothing to ensure data integrity.  The draft does mention spot
> fixes of data-at-rest methods, and in-transit methods, but there are many
> points that present areas of potential failure, and these are ignored in
> today’s implementations (at least to this commenter's knowledge).
> >
> > There is no claim made in the document that this mechanism closes all
> > integrity exposures. Can you identify particular areas that need to be
> > addressed by this mechanism but are not? Do you have specific alternative
> > proposals?
> >
> > My comment was not meant to offer an alternative solution to the
> document's proposal but rather to suggest that there are other areas of
> "integrity" that could be addressed that would result in utility.  If the
> working group finds the area interesting, this may be a potential path.
>
> The discussion in the room during IETF 105 suggested there was interest
> enough to move this document forward to publication. I thought this
> whole issue had been resolved at that time, as the conversation finished
> with an understanding that this was opaque metadata and that the next
> step was WGLC.
>
> Of the two options, IMO option 1 is the only sensible one because there
> is no citable specification of what goes in the metadata. However you've
> stated you will object if I take option 1. I don't have any strong sense
> of how to move this forward. Is there an appropriate opportunity for a
> design phone call to work all this out?
>
>
> --
> Chuck Lever
>
>
>
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