[openstack-dev] [os-brick][nova][cinder] os-brick/privsep change is done and awaiting your review

Michał Dulko michal.dulko at intel.com
Wed Feb 24 12:59:37 UTC 2016

On 02/24/2016 04:51 AM, Angus Lees wrote:
> Re: https://review.openstack.org/#/c/277224
> Most of the various required changes have flushed out by now, and this
> change now passes the dsvm-full integration tests(*).
> (*) well, the experimental job anyway.  It still relies on a
> merged-but-not-yet-released change in oslo.privsep so gate + 3rd party
> won't pass until that happens.
> What?
> This change replaces os-brick's use of rootwrap with a quick+dirty
> privsep-based drop-in replacement.  Privsep doesn't actually provide
> much security isolation when used in this way, but it *does* now run
> commands with CAP_SYS_ADMIN (still uid=0/gid=0) rather than full root
> superpowers.  The big win from a practical point of view is that it
> also means os-brick's rootwrap filters file is essentially deleted and
> no longer has to be manually merged with downstream projects.
> Code changes required in nova/cinder:
> There is one change each to nova+cinder to add the relevant
> privsep-helper command to rootwrap filters, and a devstack change to
> add a nova.conf/cinder.conf setting.  That's it - this is otherwise a
> backwards/forwards compatible change for nova+cinder.
> Deployment changes required in nova/cinder:
> A new "privsep_rootwrap.helper_command" needs to be defined in
> nova/cinder.conf (default is something sensible using sudo), and
> rootwrap filters or sudoers updated depending on the exact command
> chosen.  Be aware that any commands will now be run with CAP_SYS_ADMIN
> (only), and if that's insufficient for your hardware/drivers it can be
> tweaked with other oslo_config options.
> Risks:
> The end-result is still just running the same commands as before, via
> a different path - so there's not a lot of adventurousness here.  The
> big behavioural change is CAP_SYS_ADMIN, and (as highlighted above)
> it's conceivable that the driver for some exotic os-brick/cinder
> hardware out there wants something more than that.
> Work remaining:
> - global-requirements change needed (for os-brick) once the latest
> oslo.privsep release is made
> - cinder/nova/devstack changes need to be merged
> - after the above, the os-brick gate integration jobs will be able to
> pass, and it can be merged
> - If we want to *force* the new version of os-brick, we then need an
> appropriate global-requirements os-brick bump
> - Documentation, release notes, etc
> I'll continue chewing through those remaining work items, but
> essentially this is now in your combined hands to prioritise for
> mitaka as you deem appropriate.
>  - Gus

It seems too me that risks are higher than advantages. Moreover final
release for libraries like os.brick should happen in just 2 days and I
don't believe we have time to get every part of the job merged given how
long TODO list is.

Just my $0.02.

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