Open Stack

On 19/01, Lance Bragstad wrote:
> Hey all,
>
> I want to follow up on this thread because there's been some discussion and
> questions (some of which are in reviews) as services work through the
> proposed changes [0].
>
> TL;DR - OpenStack services implementing secure RBAC should update default
> policies with the `reader` role in a consistent manner, where it is not
> meant to protect sensitive information.
>

Hi Lance,

Thank you very much for this great summary of all the different
discussions and decisions.

I have just one question regarding your TL;DR, shouldn't it be "where it
is meant to protect sensitive information"?

As I understood it the reader should be updated so it doesn't expose
sensitive information (thus protecting it) because it's the least
privileged role.

Cheers,
Gorka.

> In the process of reviewing changes for various resources, some folks
> raised concerns about the `reader` role definition.
>
> One of the intended use-cases for implementing a `reader` role was to use
> it for auditing, as noted in the keystone definitions for each role and
> persona [1]. Another key point of that document, and the underlying design
> of secure RBAC, is that the default roles have role implications built
> between them (e.g., reader implies member, and member implies admin). This
> detail serves two important functions.
>
> First, it reduces duplication in check strings because keystone expands
> role implications in token response bodies. For example, someone with the
> `admin` role on a project will have `member` and `reader` roles in their
> token body when they authenticate for a token or validate a token. This
> reduces the complexity of our check strings by writing the policy to the
> highest level of authorization required to access an API or resource. Users
> with anything above that level will work through the role implications
> feature.
>
> Second, it reduces the need for extra role assignments. If you grant
> someone the `admin` role on a project you don't need to also give them
> `reader` and `member` role assignments. This is true regardless of how
> services implement check strings.
>
> Ultimately, the hierarchical role structure in keystone and role expansion
> in token responses give us shorter check strings and less role assignments.
> But, one thing we're aware of now is that we need to be careful how we
> expose certain information to users via the `reader` role, since it is the
> least-privileged role in the hierarchy. For example, one concern was
> exposing license key information in images to anyone with the `reader` role
> on the system. Some deployments, depending on their security posture or
> auditing targets, might not allow sensitive information to be implicitly
> exposed. Instead, they may require deployments to explicitly grant access
> to sensitive information [2].
>
> So what do we do moving forward?
>
> I think it's clear that there are APIs and resources in OpenStack that fall
> into a special category where we shouldn't expose certain information to
> the lowest level of the role hierarchy, regardless of the scope. But, the
> role implication functionality served a purpose initially to deliver a
> least-privileged role used only for read operations within a given scope. I
> think breaking that implication now is confusing considering we implemented
> the implication in Rocky [3], but I think future work for an elevated
> read-only role is a good path forward. Eventually, keystone can consider
> implementing support for a new default role, which implies `reader`, making
> all the work we do today still useful. At that time, we can update relevant
> policies to expose sensitive information with the elevated read-only role.
> I suspect this will be a much smaller set of APIs and policies. I think
> this approach strikes a balance between what we have today, and a way to
> move forward that still protects sensitive data.
>
> I proposed an update to the documentation in keystone to clarify this point
> [4]. It also doesn't assume all audits are the same. Instead, it phrases
> the ability to use `reader` roles for auditing in a way that leaves that up
> to the deployer and auditor. I think that's an important detail since
> different deployments have different security requirements. Instead of
> assuming everyone can use `reader` for auditing, we can give them a list of
> APIs they can interact with as a `reader` (or have them generate those
> policies themselves, especially if they have custom policy) and let them
> determine if that access is sufficient for their audit. If it isn't,
> deployers aren't in a worse position today, but it emphasizes the
> importance of expanding the default roles to include another tier for
> elevated read-only permissions. Given where we are in the release cycle for
> Wallaby, I don't expect keystone to implement a new default role this late
> in the release [5]. Perhaps Xena is a better target, but I'll talk with
> Kristi about it next week during the keystone meeting.
>
> I hope this helps clarify some of the confusion around the secure RBAC
> patches. If you have additional comments or questions about this topic, let
> me know. We can obviously iterate here, or use the policy pop up time slot
> which is in a couple of days [6].
>
> Thanks,
>
> Lance
>
> [0] https://review.opendev.org/q/topic:secure-rbac
> [1]
> https://docs.openstack.org/keystone/latest/admin/service-api-protection.html
> [2] FedRAMP control AC -06 (01) is an example of this - *The organization
> explicitly authorizes access to [Assignment: organization-defined security
> functions (deployed in hardware, software, and firmware) and
> security-relevant information].*
> [3] https://docs.openstack.org/releasenotes/keystone/rocky.html#new-features
> [4] https://review.opendev.org/c/openstack/keystone/+/771509
> [5] https://releases.openstack.org/wallaby/schedule.html
> [6] https://etherpad.opendev.org/p/default-policy-meeting-agenda
>
> On Thu, Dec 10, 2020 at 7:15 PM Ghanshyam Mann <gmann at ghanshyammann.com>
> wrote:
>
> >  ---- On Wed, 09 Dec 2020 14:04:57 -0600 Lance Bragstad <
> > lbragstad at gmail.com> wrote ----
> >  > Hey everyone,
> >  >
> >  > I wanted to take an opportunity to clarify some work we have been doing
> > upstream, specifically modifying the default policies across projects.
> >  >
> >  > These changes are the next phase of an initiative that’s been underway
> > since Queens to fix some long-standing security concerns in OpenStack [0].
> > For context, we have been gradually improving policy enforcement for years.
> > We started by improving policy formats, registering default policies into
> > code [1], providing better documentation for policy writers, implementing
> > necessary identity concepts in keystone [2], developing support for those
> > concepts in libraries [3][4][5][6][7][8], and consuming all of those
> > changes to provide secure default policies in a way operators can consume
> > and roll out to their users [9][10].
> >  >
> >  > All of this work is in line with some high-level documentation we
> > started writing about three years ago [11][12][13].
> >  >
> >  > There are a handful of services that have implemented the goals that
> > define secure RBAC by default, but a community-wide goal is still
> > out-of-reach. To help with that, the community formed a pop-up team with a
> > focused objective and disbanding criteria [14].
> >  >
> >  > The work we currently have in progress [15] is an attempt to start
> > applying what we have learned from existing implementations to other
> > projects. The hope is that we can complete the work for even more projects
> > in Wallaby. Most deployers looking for this functionality won't be able to
> > use it effectively until all services in their deployment support it.
> >
> > Thanks, Lance for pushing this work forwards. I completely agree and that
> > is what we get feedback in
> > forum sessions also that we should implement this in all the services
> > first before we ask operators to
> > move their cloud to the new RBAC.
> >
> > We discussed these in today's policy-popup meeting also and encourage
> > every project to help in those
> > patches to add tests and review. This will help to finish the work on
> > priority and we can provide better
> > RBAC experience to the deployer.
> >
> > -gmann
> >
> >  >
> >  >
> >  > I hope this helps clarify or explain the patches being proposed.
> >  >
> >  >
> >  > As always, I'm happy to elaborate on specific concerns if folks have
> > them.
> >  >
> >  >
> >  > Thanks,
> >  >
> >  >
> >  > Lance
> >  >
> >  >
> >  > [0] https://bugs.launchpad.net/keystone/+bug/968696/
> >  > [1]
> > https://governance.openstack.org/tc/goals/selected/queens/policy-in-code.html
> >  > [2]
> > https://specs.openstack.org/openstack/keystone-specs/specs/keystone/queens/system-scope.html
> >  > [3] https://review.opendev.org/c/openstack/keystoneauth/+/529665
> >  > [4]
> > https://review.opendev.org/c/openstack/python-keystoneclient/+/524415
> >  > [5] https://review.opendev.org/c/openstack/oslo.context/+/530509
> >  > [6] https://review.opendev.org/c/openstack/keystonemiddleware/+/564072
> >  > [7] https://review.opendev.org/c/openstack/oslo.policy/+/578995
> >  > [8]
> > https://review.opendev.org/q/topic:%22system-scope%22+(status:open%20OR%20status:merged)
> >  > [9]
> > https://review.opendev.org/q/status:merged+topic:bp/policy-defaults-refresh+branch:master
> >  > [10]
> > https://review.opendev.org/q/topic:%22implement-default-roles%22+(status:open%20OR%20status:merged)
> >  > [11]
> > https://specs.openstack.org/openstack/keystone-specs/specs/keystone/ongoing/policy-goals-and-roadmap.html
> >  > [12]
> > https://docs.openstack.org/keystone/latest/admin/service-api-protection.html
> >  > [13]
> > https://docs.openstack.org/keystone/latest/contributor/services.html#authorization-scopes
> >  > [14]
> > https://governance.openstack.org/tc/reference/popup-teams.html#secure-default-policies
> >  > [15]
> > https://review.opendev.org/q/topic:%2522secure-rbac%2522+status:open
> >  >
> >