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Re: [Nbd] [RFC PATCH] nbd-server: set supplementary groups by default when changing UID/GID



On Tue, Jul 03, 2012 at 02:51:38PM -0600, Wouter Verhelst wrote:
> On Thu, Jun 28, 2012 at 04:19:17AM +0400, Dmitry V. Levin wrote:
> > On Thu, Jun 28, 2012 at 01:15:52AM +0200, Wouter Verhelst wrote:
> > > On Mon, Jun 25, 2012 at 03:32:55AM +0400, Dmitry V. Levin wrote:
> > > > Before this change, there was no way to clear or change supplementary
> > > > groups at all, which is usually required to be done along with changing
> > > > UID and GID.  This change introduces a new global config boolean option
> > > > "setgroups" and enables it by default.  When this option is set to true,
> > > > - "group" option will additionally clear the list of supplementary groups;
> > > 
> > > This is sensible, I suppose.
> > > 
> > > > - unless "group" option is specified, "user" option will additionally
> > > >   change both GID and the list of supplementary groups to those defined
> > > >   by the given user name.
> > > 
> > > I'm not sure about that one; I think setting a group based on an option
> > > called "user" -- if there is no option "group" specified -- is going to
> > > be counterintuitive.
> > 
> > From my PoV, switching UID without switching GID and supplementary groups
> > hardly has a practical sense, so it is most likely a configuration error
> > rather than a conscious decision.
> 
> That's not the experience I've had with most daemons. I also disagree
> that this is useless; I've had situations where not switching the group
> made some sense.

Unfortunately, in situations where nbd-server processes are running with a
privileged group id and a full set of supplementary groups, these
processes usually would have write access to many more files than one
would like to allow them.

> Additionally, this changes current behaviour, which I think is even
> worse than bad defaults.
> 
> So I'm going to NAK this, I'm afraid.

Would it be acceptable to introduce the same "setgroups" option with the
same semantics but not enabled by default?


-- 
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