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On Thu, Jan 3, 2013 at 11:57 AM, Sandy Walsh <sandy.walsh at rackspace.com>wrote:

>
>
> On 01/03/2013 12:39 PM, Doug Hellmann wrote:
> >
> >
> > On Thu, Jan 3, 2013 at 11:28 AM, Mark McLoughlin <markmc at redhat.com
> > <mailto:markmc at redhat.com>> wrote:
> >
> >     On Thu, 2013-01-03 at 10:51 -0400, Sandy Walsh wrote:
> >     >
> >     > Yep, having the shared filters/weighers sounds cool.
> >     >
> >     > Is there a security concern about using the entry-point mechanism
> for
> >     > allowing untrusted code access to the rich scheduler data (host &
> >     > request info)?
> >     >
> >     > For example, someone installs a sneaky python package on a
> scheduler
> >     > node that has an entry-point that the scheduler uses. We wouldn't
> want
> >     > that to suddenly being included in the filter chain.
> >     >
> >     > The old filter driver mechanism, while clunky, was at least
> >     explicit. Or
> >     > am I missing something here?
> >
> >     Sure, it's very important that unprivileged users can't make the
> >     scheduler (or any other service) load untrusted code.
> >
> >     However, in a sanely configured system, only root or the user which
> the
> >     scheduler is running as can register an entry point. You basically
> need
> >     to be able to install a python egg in the scheduler's python path.
> >
> >
> > If the plugins are enabled explicitly through a config file, it is also
> > possible to avoid loading extra modules just because they are
> > discovered. Scanning the list of registered entry points doesn't require
> > loading their code.
>
> Thanks Doug, that's what I was looking for. Hopefully that's the default
> behaviour? It would be pretty easy to trick trick someone to install a
> "utility" python library.
>

The code that calls pkg_resources to find the entry points gets back an
EntryPoint object, which has a load() method to cause the code to be
imported. Stevedore filters plugins by name now, but after a quick review
of the code I see that it does so in a way that causes them to be loaded
before that check function is called [1]. I can fix that, and will open a
bug to do so.

Doug

[1]
https://github.com/dreamhost/stevedore/blob/master/stevedore/enabled.py#L43


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