[openstack-dev] [keystone] [nova] [oslo] [neutron][cross-project] Split Policy rules into two parts.

Salvatore Orlando sorlando at nicira.com
Thu Jun 11 21:35:11 UTC 2015

I am not able to say whether this works for Nova. Surely works for Neutron
- from a functional perspective at least.

I still don't know however whether this choice is the best way to proceed,
and perhaps you can help me understand better.

Role checks are always expressed through policy.json and can be enforced in
middleware. Does this mean that there is also a centralized policy.json, or
will we keep per-project policy files even for role checks?

Scope checks - ie: application-specific checks - can be enforced in any way
the application developers wish. They can use policy.json, be hardcoded or,
if they wish ask Pythia, the Oracle of Delphi. From an operator
perspective, this means that every project can enforce policies in a
different way. Is this going to be practical and maintainable? I can't
speak for operators, but I would like to understand a bit better what this
implies for them.


On 11 June 2015 at 17:47, Adam Young <ayoung at redhat.com> wrote:

>  Sean had a really good point when he mentioned that the Developers know
> what need to be enforced, and I think this is why he suggested that the
> base policy implementation be in Python code, not the policy JSON DSL.
> The main thrust of the dynamic policy has been to get the role-to-api
> assignment more flexible.  However, there is another side to each policy
> rule; figureing out where the project (nee' tenant) id is in the request;
> is it part of the URL, part of the request body, or in the object returned
> from the database.  This part really should be handled by the developer
> working on the policy rule, and it should not be changed.
> So...what if we say that we split policy into two checks;  a role check,
> and a scope check.  Both checks must pass in order for the user to get
> access to the API.  The Scope check is not going to be dynamic;  once set,
> they will pretty much stay set.   It might be done using the policy.json,
> or done in code, but it will be separate from the role check.
> The Neutron policy checks for things like
> "shared": "field:networks:shared=True", "shared_firewalls":
> "field:firewalls:shared=True", "shared_firewall_policies":
> "field:firewall_policies:shared=True", "shared_subnetpools":
> "field:subnetpools:shared=True",
> Would be handled by the dev teams later policy check; anything that
> requires actually fetching the object from the database is postponed to
> this stage.
> The role check will come from the policy.json file.  This will allow the
> operator to fine tune how roles are handled.  Any thing else that can be
> explicitly checked based on the token will be fair game, but not API
> specific values;  no database fetch will be performed at this point.  The
> assumption is that this policy check could be generic enough to be
> performed in middleware, and might even be enforced based on the URL
> instead of the pseudo random namespacing we do now.
> Does this suggestion work for Nova?  I think it will make the overall
> policy much easier to maintain in the field.
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