[heat][rbac] Management of "system resources" with SRBAC enforced

Rico Lin ricolin at ricolky.com
Wed Mar 9 09:20:02 UTC 2022

On Wed, Mar 9, 2022 at 1:57 PM Takashi Kajinami <tkajinam at redhat.com> wrote:
> Hello,
> I've been working on updating policy rules in heat according to the latest
> guideline for SRBAC implementation.

Thanks so much for working on it, definitely +1 on enhancing security.

>  [1]
> However this change reveals one potential issue with system resources.
> In heat there are some resource types like OS::Nova::Flavor or
> which is allowed for only system users. (I'll call these resources as
"system resources" here)

We create those resources based on checking `role:admin`, so project admin
is accepted.
This means a user under that project with role:admin, can operate those
I'm not sure what system user means here, so correct me if I'm wrong.

> Because heat uses user credentials to create resources in backend
services, if we require
> project scope for stack/resource management then we are no longer able to
create these system
> resources as part of stack. (*1)
> There are some options I can think of at this moment.
> 1. Deprecate and remove all resources which require system scope
> Pros
> - This is most easy solution to be implemented
> Cons
> - This one has the biggest user impact

Don't :)

> 2. Use service credential for resource creation
> Pros:
> - This might have smallest user impact
> Cons:
> - This requires a relatively big change in heat's architecture, which
I've not yet evaluated.
> - We need to determine the project scope role to be allowed to do system

I think this is something we can discuss more.

> 3. Implement additional project-role in each service to allow creation
via stack creation.
> Pros:
> - This would avoid user impact.
> Cons:
> - requires work in multiple components.
> - We need to determine the project scope role to be allowed to do system

Indeed current stack operation require `(role:admin and system_scope:all)
OR (role:member and project_id:%(project_id)s)`.
And if we remove the system part and keep `(role:member and
project_id:%(project_id)s)`, will mean only a user in that project with a
member role can operate stack, and if the user got also admin role, that
user can manage User/Flavor resources through stack too.

Also, note that
For the case of Nova::Flavor, both policies from Nova and Heat resource
will be enforced here, so it only accepts the intersection part of rules.

So if we go with removing the system admin, that means it's time to also
remove some deprecated global scope operation.

IMO, to accept Project Admin or member make more reasonable (like you
proposed in option 3)

> Thank you,
> Takashi
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