Secure RBAC¶
Suggested Reading¶
It is likely an understatement to say that policy enforcement is a complex subject. It requires operational context to craft custom policy to meet general use needs. Part of this is why the Secure RBAC effort was started, to provide consistency and a “good” starting place for most users who need a higher level of granularity.
That being said, it would likely help anyone working to implement customization of these policies to consult some reference material in hopes of understanding the context.
Historical Context - How we reached our access model¶
Ironic has reached the access model through an evolution the API and the data stored. Along with the data stored, the enforcement of policy based upon data stored in these fields.
System Scoped¶
System scoped authentication is intended for “administrative” activities such
as those crossing tenants/projects, as all tenants/projects should be visible
to system scoped users in Ironic.
System scoped requests do not have an associated project_id value for
the Keystone request authorization token utilized to speak with Ironic.
These requests are translated through keystonemiddleware
into values which tell Ironic what to do. Or to be more precise, tell the
policy enforcement framework the information necessary to make decisions.
System scoped requests very much align with the access controls of Ironic
before the Secure RBAC effort. The original custom role baremetal_admin
privileges are identical to a system scoped admin’s privileges.
Similarly baremetal_observer is identical to a system scoped reader.
In these concepts, the admin is allowed to create/delete objects/items.
The reader is allowed to read details about items and is intended for
users who may need an account with read-only access for or front-line support
purposes.
In addition to these concepts, a member role exists in the Secure RBAC
use model. Ironic does support this role, and in general member role
users in a system scope are able to perform basic updates/changes, with the
exception of special fields like those to disable cleaning.
Project Scoped¶
Project scoped authentication is when a request token and associated records
indicate an associated project_id value.
The Secure RBAC model, since the introduction of the base capability has been
extended as a result of an OpenStack community goal to include a manager
role in the project scope. By default, this access is equivelent to a Project
scoped admin user, however it may be delineated further as time moves
forward.
Legacy Behavior¶
The legacy behavior of API service is that all requests are treated as
project scoped requests where access is governed using an “admin project”.
This behavior is deprecated. The new behavior is a delineation of
access through system scoped and project scoped requests.
In essence, what would have served as an “admin project”, is now system
scoped usage.
Previously, Ironic API, by default, responded with access denied or permitted based upon the admin project and associated role. These responses would generate an HTTP 403 if the project was incorrect or if a user role.
Note
While Ironic has had the concept of an owner and a
lessee, they are NOT used by default. They require
custom policy configuration files to be used in the legacy
operating mode.
Supported Endpoints¶
/nodes
/nodes/<uuid>/ports
/nodes/<uuid>/portgroups
/nodes/<uuid>/volume/connectors
/nodes/<uuid>/volume/targets
/nodes/<uuid>/allocation
/ports
/portgroups
/volume/connectors
/volume/targets
/allocations
How Project Scoped Works¶
Ironic has two project use models where access is generally more delegative
to an owner and access to a lessee is generally more utilitarian.
The purpose of an owner, is more to enable the System Operator to delegate much of the administrative activity of a Node to the owner. This may be because they physically own the hardware, or they are in charge of the node. Regardless of the use model that the fields and mechanics support, these fields are to support humans, and possibly services where applicable.
The purpose of a lessee is more for a tenant in their project to be able to have access to perform basic actions with the API. In some cases that may be to reprovision or rebuild a node. Ultimately that is the lessee’s prerogative, but by default there are actions and field updates that cannot be performed by default. This is also governed by access level within a project.
These policies are applied in the way data is viewed and how data can be updated. Generally, an inability to view a node is an access permission issue in term of the project ID being correct for owner/lessee.
The ironic project has attempted to generally codify what we believe is reasonable, however operators may wish to override these policy settings. For details general policy setting details, please see Policies.
Field value visibility restrictions¶
Ironic’s API, by default has a concept of filtering node values to prevent
sensitive data from being leaked. System scoped users are subjected to basic
restrictions, whereas project scoped users are, by default, examined further
and against additional policies. This threshold is controlled with the
baremetal:node:get:filter_threshold.
By default, the following fields are masked on Nodes and are controlled by the associated policies. By default, owners are able to see insight into the infrastructure, whereas lessee users CANNOT view these fields by default.
last_error-baremetal:node:get:last_errorreservation-baremetal:node:get:reservationdriver_internal_info-baremetal:node:get:driver_internal_infodriver_info-baremetal:node:get:driver_info
Field update restrictions¶
Some of the fields in this list are restricted to System scoped users, or even only System Administrators. Some of these default restrictions are likely obvious. Owners can’t change the owner. Lessee’s can’t change the owner.
driver_info-baremetal:node:update:driver_infoproperties-baremetal:node:update:propertieschassis_uuid-baremetal:node:update:chassis_uuidinstance_uuid-baremetal:node:update:instance_uuidlessee-baremetal:node:update:lesseeowner-baremetal:node:update:ownerdriver-baremetal:node:update:driver_interfaces*_interface-baremetal:node:update:driver_interfacesnetwork_data-baremetal:node:update:network_dataconductor_group-baremetal:node:update:conductor_groupname-baremetal:node:update:nameretired-baremetal:node:update:driver_inforetired_reason-baremetal:node:update:retired
Warning
The chassis_uuid field is a write-once-only field. As such
it is restricted to system scoped administrators.
More information is available on these fields in Policies.
Allocations¶
The allocations endpoint of the API is somewhat different than other
endpoints as it allows for the allocation of physical machines to
an admin. In this context, there is not already an owner or project_id
to leverage to control access for the creation process, any project member
does have the inherent privilege of requesting an allocation. That being said,
their allocation request will require physical nodes to be owned or leased
to the project_id through the node fields owner or lessee.
Ability to override the owner is restricted to system scoped users by default
and any new allocation being requested with a specific owner, if made in
project scope, will have the project_id recorded as the owner of
the allocation.
Ultimately, an operational behavior difference exists between the owner
and lessee rights in terms of allocations. With the standard
access rights, lessee users are able to create allocations if they
own nodes which are not allocated or deployed, but they cannot reprovision
nodes when using only a member role. This limitation is not the case
for project-scoped users with the admin role.
Warning
The allocation endpoint’s use is restricted to project scoped
interactions until [oslo_policy]enforce_new_defaults has been set
to True using the baremetal:allocation:create_pre_rbac policy
rule. This is in order to prevent endpoint misuse. Afterwards all
project scoped allocations will automatically populate an owner.
System scoped request are not subjected to this restriction,
and operators may change the default restriction via the
baremetal:allocation:create_restricted policy.
Practical differences¶
Most users, upon implementing the use of system scoped authentication
should not notice a difference as long as their authentication token is
properly scoped to system and with the appropriate role for their
access level. For most users who used a baremetal project,
or other custom project via a custom policy file, along with a custom
role name such as baremetal_admin, this will require changing
the user to be a system scoped user with admin privileges.
The most noticeable difference for API consumers is the HTTP 403 access code is now mainly a HTTP 404 access code. The access concept has changed from “Does the user broadly have access to the API?” to “Does user have access to the node, and then do they have access to the specific resource?”.
What is an owner or lessee?¶
An owner or lessee is the project which has been assigned baremetal
resources. Generally these should be service projects as opposed to a project
dedicated to a specific user. This will help prevent the need to involve a
system scoped administrator from having to correct ownership records
should a project need to be removed due to an individual’s departure.
The underlying project_id is used to represent and associate the owner or
lessee.
How do I assign an owner?¶
# baremetal node set --owner <project_id> <node>
Note
With the default access policy, an owner is able to change
the assigned lessee of a node. However the lessee is unable to do
the same.
How do I assign a lessee?¶
# baremetal node set --lessee <project_id> <node>
What is the difference between an owner and lessee?¶
This is largely covered in How Project Scoped Works although
as noted it is largely in means of access. A lessee is far more
restrictive and an owner may revoke access to lessee.
Access to the underlying baremetal node is not exclusive between the
owner and lessee, and this use model expects that some level of
communication takes place between the appropriate parties.
Can I, a project admin, create a node?¶
Starting in API version 1.80, the capability was added
to allow users with an admin role to be able to create and
delete their own nodes in Ironic.
This functionality is enabled by default, and automatically
imparts owner privileges to the created Bare Metal node.
This functionality can be disabled by setting
[api]project_admin_can_manage_own_nodes to False.
