[openstack-dev] [heat][keystone] APIs, roles, request scope and admin-ness

Dolph Mathews dolph.mathews at gmail.com
Thu Nov 14 16:20:02 UTC 2013

On Sat, Nov 2, 2013 at 11:06 AM, Steven Hardy <shardy at redhat.com> wrote:

> Hi all,
> Looking to start a wider discussion, prompted by:
> https://review.openstack.org/#/c/54651/
> https://blueprints.launchpad.net/heat/+spec/management-api
> https://etherpad.openstack.org/p/heat-management-api
> Summary - it has been proposed to add a management API to Heat, similar in
> concept to the admin/public API topology used in keystone.

> I'm concerned that this may not be a pattern we want to propagate
> throughout
> OpenStack, and that for most services, we should have one API to access
> data,
> with the scope of the data returned/accessible defined by the roles held by
> the user (ie making proper use of the RBAC facilities afforded to us via
> keystone).

Agree with the concern; Identity API v3 abandons this topology in favor of
more granular access controls (policy.json) on a single API.

>From an HTTP perspective, API responses should vary according to the token
used to access the API. Literally,

  Vary: X-Auth-Token

in HTTP headers.

> In the current PoC patch, a users admin-ness is derived from the fact that
> they are accessing a specific endpoint, and that policy did not deny them
> access to that endpoint.  I think this is wrong, and we should use keystone
> roles to decide the scope of the request.

++ (although use of the word "scope" here is dangerous, as I think you mean
something different from the usual usage?)

> The proposal seems to consider tenants as the top-level of abstraction,
> with
> the next level up being a global service provider admin, but this does not
> consider the keystone v3 concept of domains [1]

v3 also allows domain-level roles to be inherited to all projects owned by
that domain, so in effect-- it does (keystone just takes care of it).

> , or that you may wish to
> provide some of these admin-ish features to domain-admin users (who will
> adminster data accross multiple tenants, just like has been proposed), via
> the
> public-facing API.
> It seems like we need a way of scoping the request (via data in the
> context),
> based on a heirarchy of admin-ness, like:
> 1. Normal user

I assume "normal" user has some "non-admin" role on a project/tenant.

> 2. Tenant Admin (has admin role in a tenant)
> 3. Domain Admin (has admin role in all tenants in the domain)

As mentioned above, keystone provides a solution to this already that other
projects don't need to be aware of.

> 4. Service Admin (has admin role everywhere, like admin_token for keystone)

admin_token is a role-free, identity-free hack. With v3, it's only
necessary for bootstrapping keystone if you're not backing to an existing
identity store, and can be removed after that.

> The current "is_admin" flag which is being used in the PoC patch won't
> allow
> this granularity of administrative boundaries to be represented, and
> splitting
> admin actions into a separate API will prevent us providing tenant and
> domain
> level admin functionality to customers in a public cloud environment.

"admin" should not be a binary thing -- in the real world it's much more
blurry. Users have a finite set of roles/attributes, some of which can be
delegated, and those roles/attributes grant the user different sets of

> It has been mentioned that in keystone, if you have admin in one tenant,
> you
> are admin everywhere, which is a pattern I think we should not follow

Good! We're working towards eliminating that, but it's been a long, slow
road. Deprecating v2 is one next step in that direction. Building a more
powerful policy engine is another. Considering identity management as "out
of scope"

> keystone folks, what are your thoughts in terms of roadmap to make role
> assignment (at the request level) scoped to tenants rather than globally
> applied?

That's how all role assignments behave today, except for the magical
"admin" role in keystone where the scope is completely ignored. Because
keystone doesn't manage resources that can are "owned by" tenants/projects
like the bulk of OpenStack does (identity management especially).

> E.g what data can we add to move from X-Roles in auth_token, to
> expressing roles in multiple tenants and domains?

Tokens can only be scoped to a single project or domain, so that's your
mapping. All X-Roles apply to the X-Project or X-Domain in context. I don't
think we have a good roadmap to support a single authenticated request with
multi-project authorization. The best solution I have is to pass an
unscoped token that can be rescoped to two or more projects as needed.
Trust-based tokens are explicitly scoped already.

> Basically, I'm very concerned that we discuss this, get a clear roadmap
> which
> will work with future keystone admin/role models, and is not a short-term
> hack
> which we won't want to maintain long-term.
> What are peoples thoughts on this?
> [1]: https://wiki.openstack.org/wiki/Domains
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