Basic Default Roles

Basic Default Roles

blueprint basic-default-roles

Managing Role Based Access Control (RBAC) across OpenStack is one of the hardest pain points for operators to deal with. It is not uncommon for operators to have to dig through source code and keep notes about oddities in RBAC implementations across OpenStack just to offer basic RBAC capabilities to their customers. End users are also affected because it is very rare for any two deployments to have similar roles, or ensure those roles are mapped to similar operations.

Problem description

OpenStack’s initial implementation of RBAC was simple and worked for trivial deployments. As OpenStack evolved and deployments started modeling larger, more complex organizations, the RBAC implementation failed to evolve with it. As a result, operators are stuck using existing tooling to provide the facade of a more sophisticated RBAC solution. This is a confusing and incredibly tough maintenance burden for operators who customize policy.

It’s not uncommon to see various services hardcode operations to a specific role. While the operation may require that role, the role to policy mapping should be driven by policy defaults that can be overridden by operators instead of hardcoding.

Proposed change

As a platform, OpenStack should offer a basic, easy to understand RBAC implementation with clear, reasonable default values. The process of implementing this will give operators more flexibility out-of-the-box. It will also be less likely to introduce inconsistencies across deployments due to the limitations of the existing implementation.

To help ensure a graceful transition, improvements were made to the oslo policy library and a community goal put in place to help projects teams register defaults policies in code and provide documentation. This work gives OpenStack project teams the tools necessary to improve default role definitions. The changing defaults can be consumed by operators in ways that are consistent with changing configuration options.

This specification proposes that Keystone enhance the basic RBAC experience by incorporating the following default roles into its default policies.

The work detailed here can be separated into two initiatives. The first is ensuring the defaults proposed are available to operators after installation. The second is incorporating those available roles into default policies across services. Note that the first initiative was targeted and completed in the Rocky release. While this specification does go into detail describing the second initiative, it will be implemented in a subsequent release (likely Stein or later). The second initiative specifically within keystone will require landing a large refactor cleaning up technical debt and moving keystone to using flask instead of a home-grown WSGI implementation. It is imperative to land this refactor prior to starting the second initiative because it will make treating RBAC across different scopes like formal business logic across the Manager layers within keystone subsystems, as opposed to obfuscating more complexity into the @controller.protected decorator that is currently used by most APIs.

Our goal is that this work will serve as a template which other services may use to adopt the proposed default roles in a future community goal.

Default Roles

reader: It should only be used for read-only APIs and operations. Alternatively referred to as readonly or observer, this role fills an extremely popular need from operators.

member: serves as the general purpose ‘do-er’ role. It introduces granularity between the administrator(s) and everyone else.

admin: This role will be only be considered appropriate for operations deemed too sensitive for anyone with a member role.

The desired outcome of implementing the roles above is that projects should start moving away from the practice of hardcoding operations to specific role names. Instead, each policy should have a reasonable default that can be overridden by operators.

Scope Type (Refresher)

project-scope: Project-scope relates to authorization for operating in a specific tenancy of the cloud.

system-scope: System-scope relates to authorization for operating with APIs that do not map nicely to the concept of Project scope. It is not meant to cover all APIs across a deployment. More information about system-scope can be found in the specification, along with relevant historical context justifying the need for system-scope.

Examples

reader: An example project-scoped application of this role would be listing project tags (identity:get_project_tags). An example system-scoped application of this role would be listing service endpoints (identity:list_endpoints).

member: An example project-scoped application of this role would be creating a project tag (identity:update_project_tags). An example system-scope application of this role would be updating an endpoint (identity:update_endpoint).

admin: An example project-scoped administrator operation would be deleting project tags (identity:delete_project_tags). An example system-scoped administrator operation would be creating an endpoint for a service (identity:create_endpoint) or listing migrations (os_compute_api:os-migrations).

The following table is neither a final nor a comprehensive list of all possible rules/policies. It serves merely as a snippet of existing rules to showcase how policies, scope, and the new default roles can work together to provide a richer policy experience.

  reader member admin
Project
  • identity:list_project_tags
  • identity:get_project_tag
  • identity:list_project_tags
  • identity:get_project_tag
  • identity:update_project_tags
  • identity:list_project_tags
  • identity:get_project_tag
  • identity:update_project_tags
  • identity:create_project_tag
  • identity:delete_project_tags
System
  • identity:list_endpoints
  • identity:get_endpoint
  • identity:list_endpoints
  • identity:get_endpoint
  • identity:update_endpoint
  • identity:list_endpoints
  • identity:get_endpoint
  • identity:update_endpoint
  • identity:create_endpoint
  • os_compute_api:os-hypervisors
  • os_compute_api:os-migrations

Example snippets of various policy files, or rendered snippets, could look like the following.

Note

The default roles discussed will be created by Keystone, during the bootstrap process, using implied roles. As indicated in the above table, having admin role implies a user also has the same rights as the member role. Therefore this user will also has the same rights as the reader role as member implies reader.

This keeps policy files clean. For example:

“identity:list_endpoints”: “role:reader OR role:member OR role:admin” is equivalent to “identity:list_endpoints”: “role:reader” as a result of the implied roles chain.

The chain of implied roles will be documented alongside of the policy-in-code defaults in addition to general Keystone documentation updates noting as much.
# scope_types = ('project')
"identity:list_project_tags": "role:reader"
"identity:get_project_tag": "role:reader"
"identity:update_project_tags": "role:member"
"identity:create_project_tag": "role:admin"
"identity:delete_project_tags": "role:admin"

# scope_types = ('system')
"identity:list_endpoints": "role:reader"
"identity:get_endpoints": "role:reader"
"identity:update_endpoint": "role:member"
"identity:create_endpoint": "role:admin"
"os_compute_api:os-hypervisors": "role:admin"
"os_compute_api:os-migrations": "role:admin"

Let’s assume the following role assignment exist:

  • Alice has role reader on system
  • Bob has the role member on system
  • Charlie has role admin on system
  • Qiana has role reader on Project Alpha
  • Rebecca has role member on Project Alpha
  • Steve has role admin on Project Alpha

Given the above assignments and policies, the following would be possible:

Alice can list or retrieve specific endpoints. Alice cannot do any project specific operations since her authorization is limited to the deployment system.

Bob can retrieve specific endpoints, list them, and update them. He cannot create new endpoints, or delete existing ones. Bob cannot do any project specific operations because his authorization is limited to the deployment system.

Charlie can retrieve specific endpoints, list, as well as create them. Additionally, Charlie can list information on migrations as well as hypervisors. He cannot perform any project specific operations because his authorization is limited to the deployment system.

Qiana can list all tags and get details about a specific tag within Project Alpha. She may not perform system specific policies because her authorization is on a single project.

Rebecca can list all tags, get details about a specific tag, and update a tag within Project Alpha. She cannot perform any system specific policies because her authorization is on a single project.

Steve can list all tags, create new tags, get details about a specific tag, update a tag, and delete tags within Project Alpha. He cannot perform any system specific policies because his authorization is on a single project.

Risk Mitigation

Scenario One – A role serving the purposes described in this spec exists under another name: Let us assume that Deployment A already has Role X which serves the purpose of the proposed here as the reader role. In this instance, it is reasonable to assume that operators may have custom policy work in place and do not want to port immediately.

This issue may be mitigated through the use of implied roles. Operators need simply to ensure that reader implies Role X. Please review the documentation on implied roles. for specific instructions on how make one role imply another.

Scenario Two – An existing ``reader``, ``member``, or ``admin`` role already exists: Let us assume that Deployment B already has a member role. Keystone will not attempt to overwrite any existing roles that have been populated. It will instead note that a role with the name member already exists in log output.

Alternatives

reader/writer/admin vs reader/member/admin. There was much debate regarding the naming conventions for these roles. We have opted to use reader, member, and admin as we believe they most accurately describe their purpose when the context of OpenStack is taken into consideration.

Implementation

Assignee(s)

Primary assignee:

Work Items

  • Add ability for Keystone bootstrap to create proposed roles
  • Implement reader role across policies
  • Implement member role across policies
  • Implement admin role across policies
  • Implement scope_types for all policies in Keystone
  • Remove @protected decorator
  • Document how operators may generate policy files with service specific roles
  • Prepare Proof-of-Concept to demo and facilitate acceptance of an OpenStack Community Goal to promote default roles across the other services.

Dependencies

This work is dependent on the following:

The work detailed in this specification will be supplemented with policy work being done in oslo and keystone:

Full dependencies and relevant work can be found in the Policy Roadmap.

Resources

Note

This work is licensed under a Creative Commons Attribution 3.0 Unported License. http://creativecommons.org/licenses/by/3.0/legalcode

Creative Commons Attribution 3.0 License

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.

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