215 lines
6.5 KiB
ReStructuredText
215 lines
6.5 KiB
ReStructuredText
.. image:: http://term.ie/data/medium_ksl.png
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:alt: Keystone
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.. toctree::
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:maxdepth 2
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Keystone is an OpenStack project that provides Identity, Token, Catalog and
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Policy services for use specifically by projects in the OpenStack family.
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Much of the design is precipitated from the expectation that the auth backends
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for most deployments will actually be shims in front of existing user systems.
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-----------
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Development
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-----------
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Setting up a development environment
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------------------------------------
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Please see the documentation under ``doc/source/`` for development setup
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(``doc/source/setup.rst``) and configuration
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(``doc/source/configuration.rst``).
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Building the Documentation
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--------------------------
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The documentation is all generated with Sphinx from within the docs directory.
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To generate the full set of HTML documentation::
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cd docs
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make autodoc
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make html
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make man
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the results are in the ``docs/build/html`` and ``docs/build/man`` directories
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respectively.
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------------
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The Services
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------------
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Keystone is organized as a group of services exposed on one or many endpoints.
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Many of these services are used in a combined fashion by the frontend, for
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example an authenticate call will validate user/tenant credentials with the
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Identity service and, upon success, create and return a token with the Token
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service.
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Identity
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--------
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The Identity service provides auth credential validation and data about Users,
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Tenants and Roles, as well as any associated metadata.
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In the basic case all this data is managed by the service, allowing the service
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to manage all the CRUD associated with the data.
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In other cases, this data is pulled, by varying degrees, from an authoritative
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backend service. An example of this would be when backending on LDAP. See
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`LDAP Backend` below for more details.
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Token
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-----
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The Token service validates and manages Tokens used for authenticating requests
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once a user/tenant's credentials have already been verified.
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Catalog
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-------
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The Catalog service provides an endpoint registry used for endpoint discovery.
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Policy
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------
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The Policy service provides a rule-based authorization engine and the
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associated rule management interface.
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----------
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Data Model
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----------
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Keystone was designed from the ground up to be amenable to multiple styles of
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backends and as such many of the methods and data types will happily accept
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more data than they know what to do with and pass them on to a backend.
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There are a few main data types:
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* **User**: has account credentials, is associated with one or more tenants
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* **Tenant**: unit of ownership in openstack, contains one or more users
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* **Role**: a first-class piece of metadata associated with many user-tenant pairs.
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* **Token**: identifying credential associated with a user or user and tenant
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* **Extras**: bucket of key-value metadata associated with a user-tenant pair.
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* **Rule**: describes a set of requirements for performing an action.
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While the general data model allows a many-to-many relationship between Users
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and Tenants and a many-to-one relationship between Extras and User-Tenant pairs,
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the actual backend implementations take varying levels of advantage of that
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functionality.
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KVS Backend
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-----------
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A simple backend interface meant to be further backended on anything that can
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support primary key lookups, the most trivial implementation being an in-memory
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dict.
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Supports all features of the general data model.
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PAM Backend
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-----------
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Extra simple backend that uses the current system's PAM service to authenticate,
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providing a one-to-one relationship between Users and Tenants with the `root`
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User also having the 'admin' role.
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Templated Backend
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-----------------
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Largely designed for a common use case around service catalogs in the Keystone
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project, a Catalog backend that simply expands pre-configured templates to
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provide catalog data.
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Example paste.deploy config (uses $ instead of % to avoid ConfigParser's
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interpolation)::
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[DEFAULT]
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catalog.RegionOne.identity.publicURL = http://localhost:$(public_port)s/v2.0
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catalog.RegionOne.identity.adminURL = http://localhost:$(public_port)s/v2.0
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catalog.RegionOne.identity.internalURL = http://localhost:$(public_port)s/v2.0
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catalog.RegionOne.identity.name = 'Identity Service'
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----------------
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Approach to CRUD
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----------------
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While it is expected that any "real" deployment at a large company will manage
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their users, tenants and other metadata in their existing user systems, a
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variety of CRUD operations are provided for the sake of development and testing.
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CRUD is treated as an extension or additional feature to the core feature set in
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that it is not required that a backend support it.
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----------------------------------
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Approach to Authorization (Policy)
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----------------------------------
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Various components in the system require that different actions are allowed
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based on whether the user is authorized to perform that action.
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For the purposes of Keystone there are only a couple levels of
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authorization being checked for:
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* Require that the performing user is considered an admin.
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* Require that the performing user matches the user being referenced.
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Other systems wishing to use the policy engine will require additional styles
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of checks and will possibly write completely custom backends. Backends included
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in Keystone are:
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Rules
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-----
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Given a list of matches to check for, simply verify that the credentials
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contain the matches. For example::
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credentials = {'user_id': 'foo', 'is_admin': 1, 'roles': ['nova:netadmin']}
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# An admin only call:
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policy_api.enforce(('is_admin:1',), credentials)
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# An admin or owner call:
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policy_api.enforce(('is_admin:1', 'user_id:foo'), credentials)
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# A netadmin call:
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policy_api.enforce(('roles:nova:netadmin',), credentials)
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Credentials are generally built from the user metadata in the 'extras' part
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of the Identity API. So, adding a 'role' to the user just means adding the role
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to the user metadata.
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Capability RBAC
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---------------
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(Not yet implemented.)
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Another approach to authorization can be action-based, with a mapping of roles
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to which capabilities are allowed for that role. For example::
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credentials = {'user_id': 'foo', 'is_admin': 1, 'roles': ['nova:netadmin']}
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# add a policy
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policy_api.add_policy('action:nova:add_network', ('roles:nova:netadmin',))
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policy_api.enforce(('action:nova:add_network',), credentials)
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In the backend this would look up the policy for 'action:nova:add_network' and
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then do what is effectively a 'Simple Match' style match against the creds.
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