On Fri, Sep 22, 2017 at 10:37 AM, Soumya Koduri <skoduri@xxxxxxxxxx> wrote:
Hi,
On 09/21/2017 07:32 PM, Pierre C wrote:
Hi All,
I would like to use glusterfs in an environment where storage servers are managed by an IT service - myself :) - and several users in the organization can mount the distributed fs. The users are root on their machines.
As far as I know about glusterfs, a root client user may impersonate any uid/gid since it provides its uid/gid itself when it talks to the bricks (like nfsv3).
The thing is, we want to enforce permissions, i.e. user X may only access files shared with him even if he's root on his machine.
I found a draft spec about glusterfs+kerberos <https://github.com/gluster/glusterfs-specs/blob/master/unde > but not much more so I think it's not possible with glusterfs right now, correct?r_review/Kerberos.md
(Also I feel that kerberos would be a bit heavy to manage)
I am not much familiar with how ssl is handled. But from what I understand from your statement above, you need to restrict root users. Isn't root-squash option enough for it?
Option: server.root-squash
Default Value: off
Description: Map requests from uid/gid 0 to the anonymous uid/gid. Note that this does not apply to any other uids or gids that might be equally sensitive, such as user bin or group staff.
Option: server.anonuid
Default Value: 65534
Description: value of the uid used for the anonymous user/nfsnobody when root-squash is enabled.
Option: server.anongid
Default Value: 65534
Description: value of the gid used for the anonymous user/nfsnobody when root-squash is enabled.
Hi Soumya,
This is not sufficient because the glusterfs protocol lets the client choose its uid/gid/groups when the client connects to a server. (done there https://github.com/gluster/glusterfs/blob/master/rpc/rpc-lib/src/auth-glusterfs.c#L177 )
So the current implementation relies on the client being trustworthy. A slightly modified client can pretend to be any user.
Do you see what I mean?
Cheers,
Pierre
eshard
Thanks,
Soumya
---
An simple hack that I found is to add custom uid/gid fields in clients' ssl certificates. The bricks use the client's uid/gid specified in its certificate rather than using one specified by the user. This solution has no effect on performance and there's no need for a central authentication.
The thing that changes is the way client certificates are generated and glusterfsd needs a small patch.
I did an experimental implementation <https://github.com/eshard/glusterfs/commit/768bf63154fdc59b > of this idea. Custom fields "1.2.3.4.5.6.7" and "1.2.3.4.5.6.8" are used for uid and gid.a67d5788743adab8679ec5ab
I tried it with custom CA trusted by all bricks and I issued a few client certificates.
No server configuration is needed when a new client is added, when a client is revoked the a CRL <https://en.wikipedia.org/wiki/Certificate_revocation_list > must updated and pushed to all servers.
By the way I didn't get glusterfs servers to accept my CRLs, do some people use it?
Notes:
* groups are not handled right now and since users may change groups regularly I don't think it would be a great idea to freeze them in a certificate. The bricks could possibly do an ldap lookup in order to retrieve and cache the groups for an uid.
* Clients obviously can't modify their certificates because they are signed by CA
What do you think of this implementation, is it safe?
Do all client operationsuse auth_glusterfs_v2_authenticate or did I miss other codepaths?
Thanks!
Pierre Carru
eshard
PS: By the way I found the source code very clean and well organized, nice job :)
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