[Gluster-devel] Portable filesystem ACLs?

[Soumya Koduri]

On 12/12/2014 11:06 PM, Niels de Vos wrote:
> Hi,
>
> I started to look into getting some form of support for ACLs in gfapi.
>
> After a short discussion with Shyam, some investigation showed that our
> current implementation of ACLs is not very portable. There definitely
> seem to be issues with ACLs when a FUSE mount is used on FreeBSD, and
> the bricks are on a Linux system.
>
> Our current implementations of (POSIX) ACLs is very much focussed on the
> Linux behaviour. For example, there is the assumption that ACLs are
> stored in the system.posix_acl_access extended attribute. FreeBSD uses a
> system.posix1e.acl_access xattr. Other platforms likely use an other
> variation. Also the (binary) encoding of the contens most definitely
> differs per platform.
>
> In order to provide a good experience with ACLs on different platforms,
> we could introduce a solution like this:
>
>      setfacl ...
>        |
>        v
>      glusterfs client (like fuse)
>        |
>        v
>      some API, possibly transparent in the posix-acl xlator
>        |       converts the client-platform specific ACL into
>        |       a Gluster ACL format
>        v
>      Outgoing RPC procedure, a new SET_ACL, or as SETXATTR(gluster.acl)
>        |
>        v
>      [network]
>        |
>        v
>      Incoming RPC procedure on the brick (can be different platform)
>        |
>        v
>      Conversion from Gluster/ACL format to platform specific, possibly in
>        |       the storage/posix xlator
>        v
>      setfacl() syscall/library call to store the ACL on the filesystem
>
>
> Reading the ACL would be the same, just in reverse.
>
> It would be most welcome to have some kind of API that can get exposed
> in gfapi, so that NFS-Ganesha and other gfapi applications can get/set
> ACLs in a standardized way. One option is to use the (possibly platform
> dependent) structures defined by libacl or librichacl.
 From a quick look at the code, 'libacl' seems to be supporting only 
'system.posix_acl_access' xattr.

IMO it may be good to have a standard 'acl_obj' structure in RichACL 
format itself, which Multi-protocol team (CCed) has been looking at & 
which you have been suggesting. This structure can be exposed to the 
applications(NFS-Ganesha/SAMBA) to fill-in ACLs data and probably call 
'glfs_set_acl(..)' which in turn converts these 'acl_obj's to platform 
dependent acl xattrs and make a syncop_setxattr call.

And in future, if we get RichACL support, we could just extend/modify 
this routine to send in those ACLs as is to the back-end.

Thanks,
Soumya

>
> What do others think about this? Any suggestions, alternative solutions
> or comments in general?
>
> Thanks,
> Niels
>
>
>
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