Re: POSIX ACL support for NFSV4 (using sideband protocol)

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

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"J. Bruce Fields" <bfields@fieldses.org> wrote on 09/02/2009 11:42:43 AM:
> On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > This patch series implement POSIX ACL support for NFSV4 clients
> > using sideband protocol.
>
> What motivates this?  Who exactly wants this and why?   What would be
> the advantages compared to other options, such as:

The most obvious reason to me is that security information
can be lost as the ACL which was generated by Linux utilities and
client acl tools (which get/set posix acls) are converted by the Linux nfs
v4 client
to NFSv4 ACLs on the wire and then the server converts them back to posix
to save them in ext3 (or ext4 or xfs etc.).  This double conversion can
result
in a different ACL returned on subsequent queries (e.g. getfacl) than the
one that the user just set.  At worst this is a security exposure and at
best it is confusing to the user (and we don't control the tools).
And Linux client to Linux server is worse than Linux client to some other
servers because of the extra conversion (which is counter intuitive)

>    - native v4 support in filesystems, or
Doesn't help now.  In the future would be nice to have something
similar to native cifs/ntfs/nfsv4 ACLs in btrfs - but that wouldn't help
for years - and won't help all of the other Linux
file systems.   CIFS and NTFS (and SMB2 in the future) could be
modified to return something like an NFSv4 ACL, but local file systems
aren't likely to change.  In the meantime we don't even have
a generalized system interface to set/get nfsv4/cifs/ntfs acls so
Linux ACL tools and libraries and server software
like Samba could be updated to handle something other than
posix ACLs.   I expect that jra and others of us on the Samba team
would love to see a few Linux file systems support CIFS/NFSv4/NTFS
ACLs but as he has reminded people - posix acls are Linux's native
ACL model.

>    - improved client-side acl tools that provided a user interface
>      for v4 acls closer to that for v3 acls, or
Problem is that ACLs are a "system feature" and the OS tools,
utilities and desktop GUI tools for Linux use POSIX ACLs since
Linux's "native acl interface" is the posix one.   It would make
sense to add a way to query the "preferred acl interface"
for a file system (and NFSv4 client could query the server
perhaps via a named attribute to determine the ACL type
preferred by the server fs).  It is important to use the
native ACL model of the server operating system
so that information is not lost unnecessarily in the conversion.

>    - a v4.x extension to add support to the main protocol?

Sounds fine to me to add an extension to the main protocol
but I doubt that it would be necessary - no extension was
formally added when v3 was extended for posix acls.
By analogy with cifs - we defined a new request and a new capability
bit for posix acl support.   CIFS ACL support is expected
("should" implement) but posix acl support is optional.  The
Linux client uses posix acls if the server claims support for it
and it has not been disabled on the client by mount option.

> > The ACL support can be disabled/enabled
> > using -o noacl/-o acl mount option. The feature enables to
> > view and  modify POSIX acls from NFSv4 client.

-- 
Thanks,

Steve

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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

On Wed, Sep 02, 2009 at 01:56:23PM -0500, Steve French wrote:
> "J. Bruce Fields" <bfields@fieldses.org> wrote on 09/02/2009 11:42:43 AM:
> > On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > > This patch series implement POSIX ACL support for NFSV4 clients
> > > using sideband protocol.
> >
> > What motivates this?  Who exactly wants this and why?   What would be
> > the advantages compared to other options, such as:
> 
> The most obvious reason to me is that security information
> can be lost as the ACL which was generated by Linux utilities and
> client acl tools (which get/set posix acls) are converted by the Linux nfs
> v4 client

The kernel v4 client doesn't do that--it passes untouched v4 acls to and
from userspace.

(We do have some patches which do that conversion in libacl, but I don't
believe any distribution has ever applied them.)

> to NFSv4 ACLs on the wire and then the server converts them back to posix
> to save them in ext3 (or ext4 or xfs etc.).  This double conversion can
> result
> in a different ACL returned on subsequent queries (e.g. getfacl) than the
> one that the user just set.

Do you have an example?  I may be forgetting some corner case, but I
don't believe there should be any, *except* for those due to name<->id
conversion.

Which is a much larger problem.

(There may also, of course, be translation problems even when only one
side is translating--but I think the id/name translation is still the
bigger problem.)

> At worst this is a security exposure and at
> best it is confusing to the user (and we don't control the tools).
> And Linux client to Linux server is worse than Linux client to some other
> servers because of the extra conversion (which is counter intuitive)
> 
> >    - native v4 support in filesystems, or
> Doesn't help now.  In the future would be nice to have something
> similar to native cifs/ntfs/nfsv4 ACLs in btrfs - but that wouldn't help
> for years - and won't help all of the other Linux
> file systems.

Here's one attempt for ext3:

	http://www.suse.de/~agruen/nfs4acl/

> CIFS and NTFS (and SMB2 in the future) could be modified to return
> something like an NFSv4 ACL, but local file systems aren't likely to
> change.

Could be.  I'd expect serious resistance, but nobody has really tried
yet that I'm aware of.

> In the meantime we don't even have
> a generalized system interface to set/get nfsv4/cifs/ntfs acls so

The current client is using raw xdr-formatted v4 acls in an extended
attribute.  We could consider some other interface if that would be more
useful to other projects.  (Andreas' patches have a different
xattr-based interface which might serve as another example.)

> Linux ACL tools and libraries and server software
> like Samba could be updated to handle something other than
> posix ACLs.   I expect that jra and others of us on the Samba team
> would love to see a few Linux file systems support CIFS/NFSv4/NTFS
> ACLs but as he has reminded people - posix acls are Linux's native
> ACL model.
> 
> >    - improved client-side acl tools that provided a user interface
> >      for v4 acls closer to that for v3 acls, or
> Problem is that ACLs are a "system feature" and the OS tools,
> utilities and desktop GUI tools for Linux use POSIX ACLs since
> Linux's "native acl interface" is the posix one.   It would make
> sense to add a way to query the "preferred acl interface"
> for a file system (and NFSv4 client could query the server
> perhaps via a named attribute to determine the ACL type
> preferred by the server fs).  It is important to use the
> native ACL model of the server operating system
> so that information is not lost unnecessarily in the conversion.
> 
> >    - a v4.x extension to add support to the main protocol?
> 
> Sounds fine to me to add an extension to the main protocol
> but I doubt that it would be necessary - no extension was
> formally added when v3 was extended for posix acls.
> By analogy with cifs - we defined a new request and a new capability
> bit for posix acl support.   CIFS ACL support is expected
> ("should" implement) but posix acl support is optional.  The
> Linux client uses posix acls if the server claims support for it
> and it has not been disabled on the client by mount option.

I'm sympathetic to this kind of argument, but it should be made at
nfsv4@ietf.org.  It will be much harder to push patches that aren't
based on something well on its way to standardization.

--b.

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Wed, Sep 2, 2009 at 3:22 PM, J. Bruce Fields<bfields@fieldses.org> wrote=
:
> On Wed, Sep 02, 2009 at 01:56:23PM -0500, Steve French wrote:
>> "J. Bruce Fields" <bfields@fieldses.org> wrote on 09/02/2009 11:42:43 AM=
:
>> > On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
>> > > This patch series implement POSIX ACL support for NFSV4 clients
>> > > using sideband protocol.
>> >
>> > What motivates this? =A0Who exactly wants this and why? =A0 What would=
 be
>> > the advantages compared to other options, such as:
>>
>> The most obvious reason to me is that security information
>> can be lost as the ACL which was generated by Linux utilities and
>> client acl tools (which get/set posix acls) are converted by the Linux n=
fs
>> v4 client
>
> The kernel v4 client doesn't do that--it passes untouched v4 acls to and
> from userspace.

1) Passing untouched ACLs doesn't help as these ACLs would be NFS specific,
and unrecognized by the default Linux tools and GUIs.  Access Control on
file and directory objects is a "system feature" - part of the OS (it has b=
een
that way since at least OS/2, not just Windows, MacOS, Solaris etc..)
 You wouldn't require the user to use different tools for modifying ACLs in
Windows, MacOS and require that the user try to figure out the ACL model of
the underlying file system before deciding what tool to use and what permis=
sions
to apply to his home directory
2) If POSIX->NFSv4 client mapping is done (as had been suggested IIRC
by others in the past) at least you lose less data (NFSv4 ACLs are "richer"
in function than POSIX ACLs - so at least with the POSIX->NFSv4->POSIX
case you are limiting the user to the subset of choices which are actually
going to be able to be stored, no inheritence etc.)




--=20
Thanks,

Steve
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Ondrej Valousek]

> 2) If POSIX->NFSv4 client mapping is done (as had been suggested IIRC
> by others in the past) at least you lose less data (NFSv4 ACLs are "richer"
> in function than POSIX ACLs - so at least with the POSIX->NFSv4->POSIX
> case you are limiting the user to the subset of choices which are actually
> going to be able to be stored, no inheritence etc.)
>
>   

I must say that I do not understand the motivation either. POSIX is not 
even a standard and should be replaced with NFSv4 acls.
Even now ext3/ext4 support NFSv4 acls (ok. patch is needed but the patch 
is there already).

If the decision was up to me, I would forbid any nfsv4 acls if the 
server can not store them properly (i.e. without any conversion) + 
forbid using nfsv4 with posix acls over sideband protocol (no standard, 
so netapp will never support this and the same is to be expected from 
Windows and Solaris). This is just adding mess and confusion.

My 5 cents...
Ondrej
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RE: POSIX ACL support for NFSV4 (using sideband protocol)

[Muntz, Daniel]

I've always thought of NFS as a means for making physical file systems
available across a network.  NFS having its own ACLs doesn't fit this
model.  E.g., "NFS ACLs" will never be integrated into NTFS.  However, I
could imagine NFS ACLs solving the general problem if they were to form
a superset of the ACLs of exportable physical file systems, and the
mechanism for interpreting ACLs for a particular physical file system
could be encoded (or modularized) in such a way that NFS' evaluation of
ACL operations has the same results as the physical file system's
execution of the same ACL operations.  You could have a POSIX ACL
module, NTFS ACL module, etc.  There's a challenge for 4.2.

ACLs could possibly be made completely opaque to NFS with a module-based
approach.

  -Dan


> -----Original Message-----
> From: Ondrej Valousek [mailto:webserv@s3group.cz] 
> Sent: Wednesday, September 02, 2009 11:20 PM
> To: Steve French
> Cc: ffilzlnx@linux.vnet.ibm.com; linux-nfs@vger.kernel.org; 
> nfsv4@linux-nfs.org; Myklebust, Trond; jra@samba.org; agruen@suse.de
> Subject: Re: POSIX ACL support for NFSV4 (using sideband protocol)
> 
> 
> > 2) If POSIX->NFSv4 client mapping is done (as had been 
> suggested IIRC 
> > by others in the past) at least you lose less data (NFSv4 
> ACLs are "richer"
> > in function than POSIX ACLs - so at least with the 
> POSIX->NFSv4->POSIX 
> > case you are limiting the user to the subset of choices which are 
> > actually going to be able to be stored, no inheritence etc.)
> >
> >   
> 
> I must say that I do not understand the motivation either. 
> POSIX is not even a standard and should be replaced with NFSv4 acls.
> Even now ext3/ext4 support NFSv4 acls (ok. patch is needed 
> but the patch is there already).
> 
> If the decision was up to me, I would forbid any nfsv4 acls 
> if the server can not store them properly (i.e. without any 
> conversion) + forbid using nfsv4 with posix acls over 
> sideband protocol (no standard, so netapp will never support 
> this and the same is to be expected from Windows and 
> Solaris). This is just adding mess and confusion.
> 
> My 5 cents...
> Ondrej
> _______________________________________________
> NFSv4 mailing list
> NFSv4@linux-nfs.org
> http://linux-nfs.org/cgi-bin/mailman/listinfo/nfsv4
> 

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Aneesh Kumar K.V]

On Thu, Sep 03, 2009 at 12:46:09AM -0700, Muntz, Daniel wrote:
> I've always thought of NFS as a means for making physical file systems
> available across a network.  NFS having its own ACLs doesn't fit this
> model.  E.g., "NFS ACLs" will never be integrated into NTFS.  However, I
> could imagine NFS ACLs solving the general problem if they were to form
> a superset of the ACLs of exportable physical file systems, and the
> mechanism for interpreting ACLs for a particular physical file system
> could be encoded (or modularized) in such a way that NFS' evaluation of
> ACL operations has the same results as the physical file system's
> execution of the same ACL operations.  You could have a POSIX ACL
> module, NTFS ACL module, etc.  There's a challenge for 4.2.
> 
> ACLs could possibly be made completely opaque to NFS with a module-based
> approach.
> 

What would be the acl model on the client side ? Considering that POSIX ACL
is looked at as the native acl model in Linux, I guess we should have the ability
to modify the ACLs using POSIX ACL tools on the nfs client

-aneesh
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Thu, Sep 3, 2009 at 2:46 AM, Muntz, Daniel<Dan.Muntz@netapp.com> wrote:
> I've always thought of NFS as a means for making physical file systems
> available across a network.  NFS having its own ACLs doesn't fit this
> model.  E.g., "NFS ACLs" will never be integrated into NTFS.  However, I
> could imagine NFS ACLs solving the general problem if they were to form
> a superset of the ACLs of exportable physical file systems

NFSv4 ACLs are similar to CIFS/NTFS ACLS. NFSv4 ACLs were
originally based on CIFS/NTFS ACLs so it would be reasonable
to export them from NTFS (although the SIDs (UUIDs) have to be mapped
to local Linux UIDs - we have user space code that can do this in Samba).
Note Samba server can map between the CIFS/NTFS and NFSv4
ACLs already and has for many years.

JRA on the Samba team and Andreas have done some good
presentations on the differences in ACL models, but other than
storing the "mask" or equivalent - POSIX ACLs can be thought of as
a subset of NFSv4/CIFS/NTFS ACLs



-- 
Thanks,

Steve

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Thu, Sep 3, 2009 at 8:54 AM, J. Bruce Fields<bfields@fieldses.org> wrote:
> On Thu, Sep 03, 2009 at 08:36:44AM -0500, Steve French wrote:
>> On Thu, Sep 3, 2009 at 2:46 AM, Muntz, Daniel<Dan.Muntz@netapp.com> wrot=
e:
>> > I've always thought of NFS as a means for making physical file systems
>> > available across a network. =A0NFS having its own ACLs doesn't fit this
>> > model. =A0E.g., "NFS ACLs" will never be integrated into NTFS. =A0Howe=
ver, I
>> > could imagine NFS ACLs solving the general problem if they were to form
>> > a superset of the ACLs of exportable physical file systems
>>
>> NFSv4 ACLs are similar to CIFS/NTFS ACLS. NFSv4 ACLs were
>> originally based on CIFS/NTFS ACLs so it would be reasonable
>> to export them from NTFS (although the SIDs (UUIDs) have to be mapped
>> to local Linux UIDs - we have user space code that can do this in Samba).
>
> On the server side, you'd actually have to map between SIDs and NFSv4
> names (strings of the form user@domain).

Yes ... We could add mapping directly from user@domain to SID - Samba
has something similar,
but we already have both mapping to/from unix uid.

1) SID (UUID, a number) to/from a local Unix UID (which winbind and
others have today)
and
2) user@domain mapped to/from local Unix UID (which NFS user space
code has today)

If


-- =

Thanks,

Steve

RE: POSIX ACL support for NFSV4 (using sideband protocol)

[David P. Quigley]

On Thu, 2009-09-03 at 00:46 -0700, Muntz, Daniel wrote:
> 
> ACLs could possibly be made completely opaque to NFS with a module-based
> approach.
> 
>   -Dan

Something to be aware of here is that once you turn a field opaque you
introduce a bunch of other issues. The MAC attribute that I've been
proposing in the IETF is mostly opaque and it has caused some problems
with interoperability. Some questions to be answered are

1) what is the initial set of modules defined? They aren't going to let
you take an opaque field and run away with it to do as you please. I've
been working on ways to define an initial set of label formats to make
the working group happier.

2) How are you going to specify these modules? It needs to be in a way
that implementors can easily use it. Are these specifications maintained
through the IETF or are they maintained by an outside organization?

3) How do modules translate between themselves. Are you going to only
allow like ACL modules to communicate? Will you have a mechanism for
those with ACL type A to still use a system with ACL type B? Will a
server be able to support both ACL type A and B? What happens if you
want both a Windows NFSv4 client and a Linux NFSv4 client to use the
same shares?

These are just some ideas to think about when you decide to make this
opaque.

Dave



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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Thu, Sep 3, 2009 at 1:20 AM, Ondrej Valousek<webserv@s3group.cz> wrote:
>
>> 2) If POSIX->NFSv4 client mapping is done (as had been suggested IIRC
>> by others in the past) at least you lose less data (NFSv4 ACLs are
>> "richer"
>> in function than POSIX ACLs - so at least with the POSIX->NFSv4->POSIX
>> case you are limiting the user to the subset of choices which are actually
>> going to be able to be stored, no inheritence etc.)
>>
> I must say that I do not understand the motivation either. POSIX is not even
> a standard and should be replaced with NFSv4 acls.
> Even now ext3/ext4 support NFSv4 acls (ok. patch is needed but the patch is
> there already).

If someone were able to convince the linux-fsdevel community to change
fs/posix_acls.c
(or add an fs/cifs_acls.c) to handle NFSv4/CIFS/NTFS ACL evaluation, and add
support to store these richer ACLs on disk for the future (e.g. for
btrfs), that would be
great - but with no local file system in kernel which can store NFSv4 ACLs and
no code to evaluate these ACLs in the VFS and with a NACK from fsdevel when
others tried this a few years ago (even after MacOS and others moved to the
CIFS/NTFS ACLs model)

> If the decision was up to me, I would forbid any nfsv4 acls if the server
> can not store them properly (i.e. without any conversion)

That would be a pretty dramatic loss of function - being forced to use
the primitive
mode bits to protect files if the server were Linux - and could be
worseeven NetApp does
some ACL mapping




-- 
Thanks,

Steve

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

On Thu, Sep 03, 2009 at 08:54:06AM -0500, Steve French wrote:
> On Thu, Sep 3, 2009 at 1:20 AM, Ondrej Valousek<webserv@s3group.cz> wrote:
> >
> >> 2) If POSIX->NFSv4 client mapping is done (as had been suggested IIRC
> >> by others in the past) at least you lose less data (NFSv4 ACLs are
> >> "richer"
> >> in function than POSIX ACLs - so at least with the POSIX->NFSv4->POSIX
> >> case you are limiting the user to the subset of choices which are actually
> >> going to be able to be stored, no inheritence etc.)
> >>
> > I must say that I do not understand the motivation either. POSIX is not even
> > a standard and should be replaced with NFSv4 acls.
> > Even now ext3/ext4 support NFSv4 acls (ok. patch is needed but the patch is
> > there already).
> 
> If someone were able to convince the linux-fsdevel community to change
> fs/posix_acls.c
> (or add an fs/cifs_acls.c) to handle NFSv4/CIFS/NTFS ACL evaluation, and add
> support to store these richer ACLs on disk for the future (e.g. for
> btrfs), that would be
> great - but with no local file system in kernel which can store NFSv4 ACLs and
> no code to evaluate these ACLs in the VFS and with a NACK from fsdevel when

I don't remember that--do you have a pointer?

--b.

> others tried this a few years ago (even after MacOS and others moved to the
> CIFS/NTFS ACLs model)
> 
> > If the decision was up to me, I would forbid any nfsv4 acls if the server
> > can not store them properly (i.e. without any conversion)
> 
> That would be a pretty dramatic loss of function - being forced to use
> the primitive
> mode bits to protect files if the server were Linux - and could be
> worseeven NetApp does
> some ACL mapping

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Thu, Sep 3, 2009 at 8:55 AM, J. Bruce Fields<bfields@fieldses.org> wrote:
> On Thu, Sep 03, 2009 at 08:54:06AM -0500, Steve French wrote:
>> if someone were able to convince the linux-fsdevel community to change
>> fs/posix_acls.c
>> (or add an fs/cifs_acls.c) to handle NFSv4/CIFS/NTFS ACL evaluation, and add
>> support to store these richer ACLs on disk for the future (e.g. for
>> btrfs), that would be
>> great - but with no local file system in kernel which can store NFSv4 ACLs and
>> no code to evaluate these ACLs in the VFS and with a NACK from fsdevel when
>
> I don't remember that--do you have a pointer?

Aneesh mentioned one strongly worded objection (I remember more resistance
from others too)

http://kerneltrap.org/mailarchive/linux-fsdevel/2006/6/24/313526



-- 
Thanks,

Steve

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

On Thu, Sep 03, 2009 at 10:35:35AM -0500, Steve French wrote:
> On Thu, Sep 3, 2009 at 8:55 AM, J. Bruce Fields<bfields@fieldses.org> wrote:
> > On Thu, Sep 03, 2009 at 08:54:06AM -0500, Steve French wrote:
> >> if someone were able to convince the linux-fsdevel community to change
> >> fs/posix_acls.c
> >> (or add an fs/cifs_acls.c) to handle NFSv4/CIFS/NTFS ACL evaluation, and add
> >> support to store these richer ACLs on disk for the future (e.g. for
> >> btrfs), that would be
> >> great - but with no local file system in kernel which can store NFSv4 ACLs and
> >> no code to evaluate these ACLs in the VFS and with a NACK from fsdevel when
> >
> > I don't remember that--do you have a pointer?
> 
> Aneesh mentioned one strongly worded objection (I remember more resistance
> from others too)
> 
> http://kerneltrap.org/mailarchive/linux-fsdevel/2006/6/24/313526

Yes, Christoph's always been vehemently opposed.  I share his distaste
for NFSv4/NT ACLs, but I agree with Trond that a solid implementation
with a demonstrated need from CIFS, NFSv4, NTFS, etc., would be likely
to overcome such objections.

--b.

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Trond Myklebust]

On Thu, 2009-09-03 at 08:54 -0500, Steve French wrote:
> If someone were able to convince the linux-fsdevel community to change
> fs/posix_acls.c
> (or add an fs/cifs_acls.c) to handle NFSv4/CIFS/NTFS ACL evaluation, and add
> support to store these richer ACLs on disk for the future (e.g. for
> btrfs), that would be
> great - but with no local file system in kernel which can store NFSv4 ACLs and
> no code to evaluate these ACLs in the VFS and with a NACK from fsdevel when
> others tried this a few years ago (even after MacOS and others moved to the
> CIFS/NTFS ACLs model)

I don't think the fs-devel community is a problem. We have native
support for plenty of these filesystems which use alternative acl
models, so a very good case can be made for their inclusion.

The main problem has been finding developers with an interest, and with
enough time on their hands. Andreas Gruenbacher started working on NFSv4
acls, but due to his time constraints, his work ended up getting farmed
out to a developer in SGI, and consequently ended up in a black hole
somewhere...

Cheers
  Trond

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Andreas Gruenbacher]

On Thursday, 3 September 2009 16:09:28 Trond Myklebust wrote:
> The main problem has been finding developers with an interest, and with
> enough time on their hands. Andreas Gruenbacher started working on NFSv4
> acls, but due to his time constraints, his work ended up getting farmed
> out to a developer in SGI, and consequently ended up in a black hole
> somewhere...

Indeed ... I transferred as much knowledge as I could to a group of SGI 
engineers who were then working on the project for a while. Unfortunately 
then the whole group was laid off (for unrelated reasons). I could not find a 
sponsor for continuing from there since.

The open issues in the project include some research (e.g., figuring out how 
Windows applications behave in practice when using Linux NFSv4 ACLs -- this 
is necessary to make a few implementation decisions which the overall design 
has left open), and some more implementation / testing / documentation work.

Thanks,
Andreas

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Thu, Sep 3, 2009 at 9:16 AM, J. Bruce Fields<bfields@fieldses.org> wrote:
> If I remember correctly, Linux's posix acl support was added at about
> the same time the NFSv4.0 spec was being written--I seem to recall the
> first ACL patches being merged around the same time as the first NFSv4
> patches?

NFSv4 RFC was December 2000 (CIFS/NTFS ACLs, which were much more
complex than earlier OS/2 ACLs,  are about 4 years earlier than NFSv4
ACLs).   POSIX ACL support was added to mainline Linux kernel at the
end of 2002 (see below):

2002/10/31 02:34:21-05:00 tytso
Port of (bugfixed) 0.8.50 acl-ext2 to 2.5

This patch adds ACL support to the ext2 filesystem.

2002/10/31 02:33:05-05:00 tytso
Port of (bugfixed) 0.8.50 acl-ext3 to 2.5.

This patch adds ACL support to the ext3 filesystem.

2002/10/31 02:30:17-05:00 tytso
Port 0.8.50 acl-xattr patch to 2.5 (harmonize header file with SGI/XFS)

This patch provides converts extended attributes passed in from user
space to a generic Posix ACL representation.



-- 
Thanks,

Steve

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Andreas Gruenbacher]

On Wednesday 02 September 2009 22:22:06 J. Bruce Fields wrote:
> On Wed, Sep 02, 2009 at 01:56:23PM -0500, Steve French wrote:
> > In the meantime we don't even have a generalized system interface to
> > set/get nfsv4/cifs/ntfs acls
> 
> The current client is using raw xdr-formatted v4 acls in an extended
> attribute.  We could consider some other interface if that would be more
> useful to other projects.  (Andreas' patches have a different
> xattr-based interface which might serve as another example.)

Yes, the current nfsv4 client exposes NFSv4 ACLs with "user@domain" and 
"group@domain" identifiers in xattrs. Users and groups of local processes and 
files are are identified by ID though, so the kernel would have to map between 
"user@domain" and "group@domain" identifiers and IDs even for local accesses. 
This doesn't make sense. The native NSFv4 ACL prototype [1] uses IDs in its 
xattr format instead; all the ID mapping logic remains in NFSv4 (and in Samba 
for CIFS).

[1] http://www.suse.de/~agruen/nfs4acl/

Andreas

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Mon, Oct 5, 2009 at 11:31 AM, Andreas Gruenbacher <agruen@suse.de> wrote:
> On Wednesday 02 September 2009 22:22:06 J. Bruce Fields wrote:
>> On Wed, Sep 02, 2009 at 01:56:23PM -0500, Steve French wrote:
>> > In the meantime we don't even have a generalized system interface to
>> > set/get nfsv4/cifs/ntfs acls
>>
>> The current client is using raw xdr-formatted v4 acls in an extended
>> attribute.  We could consider some other interface if that would be more
>> useful to other projects.  (Andreas' patches have a different
>> xattr-based interface which might serve as another example.)
>
> Yes, the current nfsv4 client exposes NFSv4 ACLs with "user@domain" and
> "group@domain" identifiers in xattrs. Users and groups of local processes and
> files are are identified by ID though, so the kernel would have to map between
> "user@domain" and "group@domain" identifiers and IDs even for local accesses.
> This doesn't make sense. The native NSFv4 ACL prototype [1] uses IDs in its
> xattr format instead; all the ID mapping logic remains in NFSv4 (and in Samba
> for CIFS).
>
> [1] http://www.suse.de/~agruen/nfs4acl/

Recently I looked through NFSv4.1 spec, and it seems to address some
ACL incompatibilities (with CIFS) by extending the NFSv4 ACL model.

Should we be aiming for an eventual interface that would work for NFSv4.1
or limiting it to current NFSv4?

Any idea on the state of NFSv4.1 it seems to be stuck for almost a year?


-- 
Thanks,

Steve

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Andreas Gruenbacher]

On Monday 05 October 2009 18:44:34 Steve French wrote:
> Recently I looked through NFSv4.1 spec, and it seems to address some
> ACL incompatibilities (with CIFS) by extending the NFSv4 ACL model.
> 
> Should we be aiming for an eventual interface that would work for NFSv4.1
> or limiting it to current NFSv4?

I think Automatic Inheritance [*] is important for current Windows clients:
without it it's basically impossible to manage the permissions of entire
directory trees without shooting yourself in the foot.

[*] http://www.nfsv4-editor.org/draft-25/draft-ietf-nfsv4-minorversion1-25.html#auto_inherit

> Any idea on the state of NFSv4.1 it seems to be stuck for almost a year?

Sorry, don't know.

Andreas
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

On Mon, Oct 5, 2009 at 12:09 PM, Andreas Gruenbacher <agruen@suse.de> wrote:
> On Monday 05 October 2009 18:44:34 Steve French wrote:
>> Recently I looked through NFSv4.1 spec, and it seems to address some
>> ACL incompatibilities (with CIFS) by extending the NFSv4 ACL model.
>>
>> Should we be aiming for an eventual interface that would work for NFSv4.1
>> or limiting it to current NFSv4?
>
> I think Automatic Inheritance [*] is important for current Windows clients:
> without it it's basically impossible to manage the permissions of entire
> directory trees without shooting yourself in the foot.

Yes - that piece among the various NFSv41 ACL changes also
jumped out to me as I scanned the NFSv4.1 summary ... in part
because I was looking at some Samba mapping problems (CIFS to NFSv4
ACLs) recently.   In any case, seems very useful (even without
any CIFS compatibility issues).


-- 
Thanks,

Steve
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Steve French]

"J. Bruce Fields" <bfields@fieldses.org> wrote on 09/02/2009 11:42:43 AM:
> On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > This patch series implement POSIX ACL support for NFSV4 clients
> > using sideband protocol.
>
> What motivates this?  Who exactly wants this and why?   What would be
> the advantages compared to other options, such as:

The most obvious reason to me is that security information
can be lost as the ACL which was generated by Linux utilities and
client acl tools (which get/set posix acls) are converted by the Linux
nfs v4 client
to NFSv4 ACLs on the wire and then the server converts them back to posix
to save them in ext3 (or ext4 or xfs etc.).  This double conversion can result
in a different ACL returned on subsequent queries (e.g. getfacl) than the
one that the user just set.  At worst this is a security exposure and at
best it is confusing to the user (and we don't control the tools).
And Linux client to Linux server is worse than Linux client to some other
servers because of the extra conversion (which is counter intuitive)

>    - native v4 support in filesystems, or
Doesn't help now.  In the future would be nice to have something
similar to native cifs/ntfs/nfsv4 ACLs in btrfs - but that wouldn't help
for years - and won't help all of the other Linux
file systems.   CIFS and NTFS (and SMB2 in the future) could be
modified to return something like an NFSv4 ACL, but local file systems
aren't likely to change.  In the meantime we don't even have
a generalized system interface to set/get nfsv4/cifs/ntfs acls so
Linux ACL tools and libraries and server software
like Samba could be updated to handle something other than
posix ACLs.   I expect that jra and others of us on the Samba team
would love to see a few Linux file systems support CIFS/NFSv4/NTFS
ACLs but as he has reminded people - posix acls are Linux's native
ACL model.

>    - improved client-side acl tools that provided a user interface
>      for v4 acls closer to that for v3 acls, or
Problem is that ACLs are a "system feature" and the OS tools,
utilities and desktop GUI tools for Linux use POSIX ACLs since
Linux's "native acl interface" is the posix one.   It would make
sense to add a way to query the "preferred acl interface"
for a file system (and NFSv4 client could query the server
perhaps via a named attribute to determine the ACL type
preferred by the server fs).  It is important to use the
native ACL model of the server operating system
so that information is not lost unnecessarily in the conversion.

>    - a v4.x extension to add support to the main protocol?

Sounds fine to me to add an extension to the main protocol
but I doubt that it would be necessary - no extension was
formally added when v3 was extended for posix acls.
By analogy with cifs - we defined a new request and a new capability
bit for posix acl support.   CIFS ACL support is expected
("should" implement) but posix acl support is optional.  The
Linux client uses posix acls if the server claims support for it
and it has not been disabled on the client by mount option.

> > The ACL support can be disabled/enabled
> > using -o noacl/-o acl mount option. The feature enables to
> > view and  modify POSIX acls from NFSv4 client.


--
Thanks,

Steve

POSIX ACL support for NFSV4 (using sideband protocol)

[Aneesh Kumar K.V]

This patch series implement POSIX ACL support for NFSV4 clients
using sideband protocol. The ACL support can be disabled/enabled
using -o noacl/-o acl mount option. The feature enables to
view and  modify POSIX acls from NFSv4 client.

-aneesh

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> This patch series implement POSIX ACL support for NFSV4 clients
> using sideband protocol.

What motivates this?  Who exactly wants this and why?   What would be
the advantages compared to other options, such as:

	- native v4 support in filesystems, or
	- improved client-side acl tools that provided a user interface
	  for v4 acls closer to that for v3 acls, or
	- a v4.x extension to add support to the main protocol?

Is there interest in implementing this on any OS other than linux, or
would this be a linux-only extension for the forseeable future?

What sideband protocol exactly?  If it's exactly the same protocol as
the one used with v3, there must be some slight mismatches: e.g. v4
filehandles are allowed to be longer.  How do you deal with these?

--b.

> The ACL support can be disabled/enabled
> using -o noacl/-o acl mount option. The feature enables to
> view and  modify POSIX acls from NFSv4 client.
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Aneesh Kumar K.V]

On Wed, Sep 02, 2009 at 12:42:43PM -0400, J. Bruce Fields wrote:
> On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > This patch series implement POSIX ACL support for NFSV4 clients
> > using sideband protocol.
> 
> What motivates this?  Who exactly wants this and why?   What would be
> the advantages compared to other options, such as:
> 
> 	- native v4 support in filesystems, or
> 	- improved client-side acl tools that provided a user interface
> 	  for v4 acls closer to that for v3 acls, or
> 	- a v4.x extension to add support to the main protocol?
> 
> Is there interest in implementing this on any OS other than linux, or
> would this be a linux-only extension for the forseeable future?
> 
> What sideband protocol exactly?  If it's exactly the same protocol as
> the one used with v3, there must be some slight mismatches: e.g. v4
> filehandles are allowed to be longer.  How do you deal with these?
> 

It is similar to v3 with longer file handle. Also it doesn't support
attribute update as a part of the acl calls. I does zap cache and expect
the client to do another call to get the updated attribute values. Primary
motivation is to avoid side band rpc having to handle compound request so
that we can keep it simple.

-aneesh

Re: POSIX ACL support for NFSV4 (using sideband protocol)

[J. Bruce Fields]

On Wed, Sep 02, 2009 at 11:19:57PM +0530, Aneesh Kumar K.V wrote:
> On Wed, Sep 02, 2009 at 12:42:43PM -0400, J. Bruce Fields wrote:
> > On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > > This patch series implement POSIX ACL support for NFSV4 clients
> > > using sideband protocol.
> > 
> > What motivates this?  Who exactly wants this and why?   What would be
> > the advantages compared to other options, such as:
> > 
> > 	- native v4 support in filesystems, or
> > 	- improved client-side acl tools that provided a user interface
> > 	  for v4 acls closer to that for v3 acls, or
> > 	- a v4.x extension to add support to the main protocol?
> > 
> > Is there interest in implementing this on any OS other than linux, or
> > would this be a linux-only extension for the forseeable future?
> > 
> > What sideband protocol exactly?  If it's exactly the same protocol as
> > the one used with v3, there must be some slight mismatches: e.g. v4
> > filehandles are allowed to be longer.  How do you deal with these?
> > 
> 
> It is similar to v3 with longer file handle.  Also it doesn't support
> attribute update as a part of the acl calls. I does zap cache and expect
> the client to do another call to get the updated attribute values. Primary
> motivation is to avoid side band rpc having to handle compound request so
> that we can keep it simple.

That doesn't really answer the "motivation" question.

If you really want to do this, writing the code is the easy part.  The
really (extremely) hard part is coming up with good answers to the
questions above.

--b.
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Re: POSIX ACL support for NFSV4 (using sideband protocol)

[Andreas Gruenbacher]

On Wednesday, 2 September 2009 18:42:43 J. Bruce Fields wrote:
> On Wed, Sep 02, 2009 at 05:54:20PM +0530, Aneesh Kumar K.V wrote:
> > This patch series implement POSIX ACL support for NFSV4 clients
> > using sideband protocol.
>
> What motivates this?  Who exactly wants this and why?   What would be
> the advantages compared to other options, such as:
>
> 	- native v4 support in filesystems, or
> 	- improved client-side acl tools that provided a user interface
> 	  for v4 acls closer to that for v3 acls, or
> 	- a v4.x extension to add support to the main protocol?

I can't speak for Aneesh, but my expectation is that we'll get native NFSv4 
ACL support eventually, just maybe not in the next few years. Even then, 
systems with native POSIX ACLs will coexist with machines with native NFSv4 
ACLs for a long time, and so NFSv4's lack of decent support for POSIX ACLs is 
a major problem.

I'm not sure what you mean by improved client-side tool. Some information is 
unrecoverably lost when POSIX ACLs are converted into NFSv4 ACLs; no tool on 
the client can make up for this. Besides, presenting server-side POSIX ACLs 
as similar (but not quite identical) NFSv4 ACLs on the client is really not a 
good idea: right now, clients can only guess which NFSv4 ACLs are actually 
POSIX ACLs in disguise.

> Is there interest in implementing this on any OS other than linux, or
> would this be a linux-only extension for the forseeable future?

Good question. I would sure prefer a standard solution to a Linux specific 
hack -- but that being said, I would prefer a solution to the current 
mess ;-)

Thanks,
Andreas
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