Open Stack

On 05/22/2018 09:08 AM, Luke Hinds wrote:
> 
> 
> On Tue, May 22, 2018 at 5:27 AM, Cédric Jeanneret <cjeanner at redhat.com
> <mailto:cjeanner at redhat.com>> wrote:
> 
> 
> 
>     On 05/21/2018 03:49 PM, Luke Hinds wrote:
>     > A few operators have requested if its possible to limit sudo's coverage
>     > on both the under / overcloud. There is concern over `ALL=(ALL)
>     > NOPASSWD:ALL` , which allows someone to  `sudo su`.
>     > 
>     > This task has come under the care of the tripleo security squad.
>     > 
>     > The work is being tracked and discussed here [0].
>     > 
>     > So far it looks like the approach will be to use regexp within
>     > /etc/sudoers.d/*., to narrow down as close as possible to the specific
>     > commands called. Some services already do this with rootwrap:
>     > 
>     > ironic ALL = (root) NOPASSWD: /usr/bin/ironic-rootwrap
>     > /etc/ironic/rootwrap.conf *   
>     > 
>     > It's fairly easy to pick up a list of all sudo calls using a simple
>     > script [1]
>     > 
>     > The other prolific user of sudo is ansible / stack, for example:
>     > 
>     > /bin/sh -c echo BECOME-SUCCESS-kldpbeueyodisjajjqthpafzadrncdff;
>     > /usr/bin/python
>     > /home/stack/.ansible/tmp/ansible-tmp-1526579105.0-109863952786117/systemd.py;
>     > rm -rf
>     > "/home/stack/.ansible/tmp/ansible-tmp-1526579105.0-109863952786117/" >
>     > /dev/null 2>&1
>     > 
>     > My feelings here are to again use regexp around the immutable non random
>     > parts of the command.  cjeanner also made some suggestions in the
>     > etherpad [0].
> 
>     Might be a temporary way to limit the surface indeed, but an upstream
>     change in Ansible would still be really nice. Predictable names is the
>     only "right" way, although this will create a long sudo ruleset. A
>     really long one to be honnest. Maintainability is also to be discussed
>     in either way (maintain a couple of regexp vs 200+ rules.. hmmm).
> 
> 
> As I understand it, the problem with predicable names is they also
> become predictable to attackers (this would be the reason ansible adds
> in the random string). It helps prevent someone creating a race
> condition to replace the python script with something more nefarious.
> Its the same reason commands such as mktemp exists.

Fair enough indeed. Both solution have their pros and cons. In order to
move on, I think the regexp in sudoers is acceptable for the following
reasons:
- limits accesses outside of ansible generated code
- allows others to still push new content without having to change sudo
listing (thanks to regexp)
- still hard to inject bad things in the executed script/code
- quick to implement (well, fastest than requiring an upstream change
that will most probably break some internal things before working
properly, and without adding more security as you explained it)

@Juan do you agree with that statement? As we had some quick chat about it.

Note: I'm not part of the security squad ;). But I like secured things.

> 
>     > 
>     > However aside to the approach, we need to consider the impact locking
>     > down might have should someone create a develop a new bit of code that
>     > leverages commands wrapped in sudo and assumes ALL with be in place.
>     > This of course will be blocked.
> 
>     This will indeed require some doc, as this is a "major" change. However,
>     the use of regexp should somewhat limit the impact, especially since
>     Ansible pushes its exec script in the same location.
>     Even new parts should be allowed (that might be a bit of concern if we
>     want to really dig in the consequences of a bad template being injected
>     in some way [looking config-download ;)]).
>     But at some point, we might also decide to let the OPs ensure their
>     infra isn't compromised.
>     Always the same thread-of with Security vs The World - convenience vs
>     cumbersome management, and so on.
> 
>     >
>     > Now my guess is that our CI would capture this as the deploy would
>     > fail(?) and the developer should work out an entry is needed when
>     > testing their patch, but wanted to open this up to others who know
>     > testing at gate better much better than myself.  Also encourage any
>     > thoughts on the topic to be introduced to the etherpad [0]
>     >
>     > [0] https://etherpad.openstack.org/p/tripleo-heat-admin-security
>     <https://etherpad.openstack.org/p/tripleo-heat-admin-security>
>     > [1]
>     https://gist.github.com/lukehinds/4cdb1bf4de526a049c51f05698b8b04f
>     <https://gist.github.com/lukehinds/4cdb1bf4de526a049c51f05698b8b04f>
>     >
>     > --
>     > Luke Hinds
> 
>     -- 
>     Cédric Jeanneret
>     Software Engineer
>     DFG:DF
> 
> 
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> 
> 
> 
> -- 
> Luke Hinds | NFV Partner Engineering | CTO Office | Red Hat
> e: lhinds at redhat.com <mailto:lhinds at redhat.com> | irc: lhinds @freenode
> |t: +44 12 52 36 2483
> 
> 
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-- 
Cédric Jeanneret
Software Engineer
DFG:DF

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