swift/doc/source/overview_auth.rst

===============
The Auth System
===============

--------
Overview
--------

Swift supports a number of auth systems that share the following common
characteristics:

* The authentication/authorization part can be an external system or a
  subsystem run within Swift as WSGI middleware
* The user of Swift passes in an auth token with each request
* Swift validates each token with the external auth system or auth subsystem
  and caches the result
* The token does not change from request to request, but does expire

The token can be passed into Swift using the X-Auth-Token or the
X-Storage-Token header. Both have the same format: just a simple string
representing the token. Some auth systems use UUID tokens, some an MD5 hash of
something unique, some use "something else" but the salient point is that the
token is a string which can be sent as-is back to the auth system for
validation.

Swift will make calls to the auth system, giving the auth token to be
validated. For a valid token, the auth system responds with an overall
expiration time in seconds from now. To avoid the overhead in validating the same
token over and over again, Swift will cache the
token for a configurable time, but no longer than the expiration
time.

The Swift project includes two auth systems:

- :ref:`temp_auth`
- :ref:`keystone_auth`

It is also possible to write your own auth system as described in
:ref:`extending_auth`.

.. _temp_auth:

--------
TempAuth
--------

TempAuth is used primarily in Swift's functional test environment and can be
used in other test environments (such as :doc:`development_saio`). It is not
recommended to use TempAuth in a production system. However, TempAuth is fully
functional and can be used as a model to develop your own auth system.

TempAuth has the concept of admin and non-admin users
within an account.  Admin users can do anything within the account.
Non-admin users can only perform read operations. However, some
privileged metadata such as X-Container-Sync-Key is not accessible to
non-admin users.

Users with the special group ``.reseller_admin`` can operate on any account.
For an example usage please see :mod:`swift.common.middleware.tempauth`.
If a request is coming from a reseller the auth system sets the request environ
reseller_request to True. This can be used by other middlewares.

Other users may be granted the ability to perform operations on
an account or container via ACLs. TempAuth supports two types of ACL:

- Per container ACLs based on the
  container's ``X-Container-Read`` and ``X-Container-Write`` metadata. See
  :ref:`container_acls` for more information.

- Per account ACLs based on the account's ``X-Account-Access-Control``
  metadata. For more information see :ref:`account_acls`.

TempAuth will now allow OPTIONS requests to go through without a token.

The TempAuth middleware is responsible for creating its own tokens. A user
makes a request containing their username and password and TempAuth
responds with a token. This token is then used to perform subsequent
requests on the user's account, containers and objects.

.. _keystone_auth:

-------------
Keystone Auth
-------------

Swift is able to authenticate against OpenStack Keystone_. In this
environment, Keystone is responsible for creating and validating
tokens. The :ref:`keystoneauth` middleware is responsible for
implementing the auth system within Swift as described here.

The :ref:`keystoneauth` middleware supports per container based ACLs on the
container's ``X-Container-Read`` and ``X-Container-Write`` metadata.
For more information see :ref:`container_acls`.

The account-level ACL is not supported by Keystone auth.

In order to use the ``keystoneauth`` middleware the ``auth_token``
middleware from KeystoneMiddleware_ will need to be configured.

The ``authtoken`` middleware performs the authentication token
validation and retrieves actual user authentication information. It
can be found in the KeystoneMiddleware_ distribution.

The :ref:`keystoneauth` middleware performs authorization and mapping the
Keystone roles to Swift's ACLs.

.. _KeystoneMiddleware: https://docs.openstack.org/keystonemiddleware/latest/
.. _Keystone: https://docs.openstack.org/keystone/latest/

.. _configuring_keystone_auth:

Configuring Swift to use Keystone
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Configuring Swift to use Keystone_
is relatively straightforward.  The first
step is to ensure that you have the ``auth_token`` middleware installed. It can
either be dropped in your python path or installed via the KeystoneMiddleware_
package.

You need at first make sure you have a service endpoint of type
``object-store`` in Keystone pointing to your Swift proxy. For example
having this in your ``/etc/keystone/default_catalog.templates`` ::

  catalog.RegionOne.object_store.name = Swift Service
  catalog.RegionOne.object_store.publicURL = http://swiftproxy:8080/v1/AUTH_$(tenant_id)s
  catalog.RegionOne.object_store.adminURL = http://swiftproxy:8080/
  catalog.RegionOne.object_store.internalURL = http://swiftproxy:8080/v1/AUTH_$(tenant_id)s

On your Swift proxy server you will want to adjust your main pipeline
and add auth_token and keystoneauth in your
``/etc/swift/proxy-server.conf`` like this ::

  [pipeline:main]
  pipeline = [....] authtoken keystoneauth proxy-logging proxy-server

add the configuration for the authtoken middleware::

  [filter:authtoken]
  paste.filter_factory = keystonemiddleware.auth_token:filter_factory
  www_authenticate_uri = http://keystonehost:5000/
  auth_url = http://keystonehost:5000/
  auth_plugin = password
  project_domain_id = default
  user_domain_id = default
  project_name = service
  username = swift
  password = password
  cache = swift.cache
  include_service_catalog = False
  delay_auth_decision = True

The actual values for these variables will need to be set depending on
your situation, but in short:

* ``www_authenticate_uri`` should point to a Keystone service from which users may
  retrieve tokens. This value is used in the `WWW-Authenticate` header that
  auth_token sends with any denial response.
* ``auth_url`` points to the Keystone Admin service. This information is
  used by the middleware to actually query Keystone about the validity of the
  authentication tokens. It is not necessary to append any Keystone API version
  number to this URI.
* The auth credentials (``project_domain_id``, ``user_domain_id``,
  ``username``, ``project_name``, ``password``) will be used to retrieve an
  admin token. That token will be used to authorize user tokens behind the
  scenes. These credentials must match the Keystone credentials for the Swift
  service. The example values shown here assume a user named 'swift' with admin
  role on a project named 'service', both being in the Keystone domain with id
  'default'. Refer to the `KeystoneMiddleware documentation
  <https://docs.openstack.org/keystonemiddleware/latest/middlewarearchitecture.html#configuration>`_
  for other examples.

* ``cache`` is set to ``swift.cache``. This means that the middleware
  will get the Swift memcache from the request environment.
* ``include_service_catalog`` defaults to ``True`` if not set. This means
  that when validating a token, the service catalog is retrieved
  and stored in the ``X-Service-Catalog`` header. This is required if you use
  access-rules in Application Credentials. You may also need to increase
  `max_header_size`.


.. note::

    The authtoken config variable ``delay_auth_decision`` must be set to
    ``True``. The default is ``False``, but that breaks public access,
    :ref:`staticweb`, :ref:`formpost`, :ref:`tempurl`, and authenticated
    capabilities requests (using :ref:`discoverability`).

and you can finally add the keystoneauth configuration. Here is a simple
configuration::

  [filter:keystoneauth]
  use = egg:swift#keystoneauth
  operator_roles = admin, swiftoperator

Use an appropriate list of roles in operator_roles. For example, in
some systems, the role ``_member_`` or ``Member`` is used to indicate
that the user is allowed to operate on project resources.

OpenStack Service Using Composite Tokens
----------------------------------------

Some OpenStack services such as Cinder and Glance may use
a "service account". In this mode, you configure a separate account where
the service stores project data that it manages. This account is not used
directly by the end-user. Instead, all access is done through the service.

To access the "service" account, the service must present two tokens: one from
the end-user and another from its own service user. Only when both tokens are
present can the account be accessed. This section describes how to set the
configuration options to correctly control access to both the "normal" and
"service" accounts.

In this example, end users use the ``AUTH_`` prefix in account names,
whereas services use the ``SERVICE_`` prefix::

  [filter:keystoneauth]
  use = egg:swift#keystoneauth
  reseller_prefix = AUTH, SERVICE
  operator_roles = admin, swiftoperator
  SERVICE_service_roles = service

The actual values for these variable will need to be set depending on your
situation as follows:

* The first item in the reseller_prefix list must match Keystone's endpoint
  (see ``/etc/keystone/default_catalog.templates`` above). Normally
  this is ``AUTH``.
* The second item in the reseller_prefix list is the prefix used by the
  OpenStack services(s). You must configure this value (``SERVICE`` in the
  example) with whatever the other OpenStack service(s) use.
* Set the operator_roles option to contain a role or roles that end-user's
  have on project's they use.
* Set the SERVICE_service_roles value to a role or roles that only the
  OpenStack service user has. Do not use a role that is assigned to
  "normal" end users. In this example, the role ``service`` is used.
  The service user is granted this role to a *single* project only. You do
  not need to make the service user a member of every project.

This configuration works as follows:

* The end-user presents a user token to an OpenStack service. The service
  then makes a Swift request to the account with the ``SERVICE`` prefix.
* The service forwards the original user token with the request. It also
  adds it's own service token.
* Swift validates both tokens. When validated, the user token gives the
  ``admin`` or ``swiftoperator`` role(s). When validated, the service token
  gives the ``service`` role.
* Swift interprets the above configuration as follows:

  * Did the user token provide one of the roles listed in operator_roles?
  * Did the service token have the ``service`` role as described by the
    ``SERVICE_service_roles`` options.

* If both conditions are met, the request is granted. Otherwise, Swift
  rejects the request.

In the above example, all services share the same account. You can separate
each service into its own account. For example, the following provides a
dedicated account for each of the Glance and Cinder services. In addition,
you must assign the ``glance_service`` and ``cinder_service`` to the
appropriate service users::

  [filter:keystoneauth]
  use = egg:swift#keystoneauth
  reseller_prefix = AUTH, IMAGE, VOLUME
  operator_roles = admin, swiftoperator
  IMAGE_service_roles = glance_service
  VOLUME_service_roles = cinder_service


Access control using keystoneauth
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

By default the only users able to perform operations (e.g. create a container)
on an account are those having a Keystone role for the corresponding Keystone
project that matches one of the roles specified in the ``operator_roles``
option.

Users who have one of the ``operator_roles`` will be able to set container ACLs
to grant other users permission to read and/or write objects in specific
containers, using ``X-Container-Read`` and ``X-Container-Write`` headers
respectively. In addition to the ACL formats described
:mod:`here <swift.common.middleware.acl>`, keystoneauth supports ACLs using the
format::

 other_project_id:other_user_id.

where ``other_project_id`` is the UUID of a Keystone project and
``other_user_id`` is the UUID of a Keystone user. This will allow the other
user to access a container provided their token is scoped on the other
project. Both ``other_project_id`` and ``other_user_id`` may be replaced with
the wildcard character ``*`` which will match any project or user respectively.

Be sure to use Keystone UUIDs rather than names in container ACLs.

.. note::

    For backwards compatibility, keystoneauth will by default grant container
    ACLs expressed as ``other_project_name:other_user_name`` (i.e. using
    Keystone names rather than UUIDs) in the special case when both the other
    project and the other user are in Keystone's default domain and the project
    being accessed is also in the default domain.

    For further information see :ref:`keystoneauth`

Users with the Keystone role defined in ``reseller_admin_role``
(``ResellerAdmin`` by default) can operate on any account. The auth system
sets the request environ reseller_request to True if a request is coming
from a user with this role. This can be used by other middlewares.

Troubleshooting tips for keystoneauth deployment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some common mistakes can result in API requests failing when first deploying
keystone with Swift:

* Incorrect configuration of the Swift endpoint in the Keystone service.

  By default, keystoneauth expects the account part of a URL to have the form
  ``AUTH_<keystone_project_id>``. Sometimes the ``AUTH_`` prefix is missed when
  configuring Swift endpoints in Keystone, as described in the `Install  Guide
  <http://docs.openstack.org/>`_. This is easily diagnosed by inspecting the
  proxy-server log file for a failed request URL and checking that the URL
  includes the ``AUTH_`` prefix (or whatever reseller prefix may have been
  configured for keystoneauth)::

      GOOD:
      proxy-server: 127.0.0.1 127.0.0.1 07/Sep/2016/16/06/58 HEAD /v1/AUTH_cfb8d9d45212408b90bc0776117aec9e HTTP/1.0 204 ...

      BAD:
      proxy-server: 127.0.0.1 127.0.0.1 07/Sep/2016/16/07/35 HEAD /v1/cfb8d9d45212408b90bc0776117aec9e HTTP/1.0 403 ...


* Incorrect configuration of the ``authtoken`` middleware options in the Swift
  proxy server.

  The ``authtoken`` middleware communicates with the Keystone service to
  validate tokens that are presented with client requests. To do this
  ``authtoken`` must authenticate itself with Keystone using the credentials
  configured in the ``[filter:authtoken]`` section of
  ``/etc/swift/proxy-server.conf``. Errors in these credentials can result in
  ``authtoken`` failing to validate tokens and may be revealed in the proxy
  server logs by a message such as::

      proxy-server: Identity server rejected authorization

  .. note::

      More detailed log messaging may be seen by setting the ``authtoken``
      option ``log_level = debug``.

  The ``authtoken`` configuration options may be checked by attempting to use
  them to communicate directly with Keystone using an ``openstack`` command
  line. For example, given the ``authtoken`` configuration sample shown in
  :ref:`configuring_keystone_auth`, the following command should return a
  service catalog::

      openstack --os-identity-api-version=3 --os-auth-url=http://keystonehost:5000/ \
          --os-username=swift --os-user-domain-id=default \
          --os-project-name=service --os-project-domain-id=default \
          --os-password=password catalog show object-store

  If this ``openstack`` command fails then it is likely that there is a problem
  with the ``authtoken`` configuration.

.. _extending_auth:

--------------
Extending Auth
--------------

TempAuth is written as wsgi middleware, so implementing your own auth is as
easy as writing new wsgi middleware, and plugging it in to the proxy server.

See :doc:`development_auth` for detailed information on extending the
auth system.