219 lines
9.7 KiB
ReStructuredText
219 lines
9.7 KiB
ReStructuredText
===============
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The Auth System
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===============
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--------
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TempAuth
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--------
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The auth system for Swift is loosely based on the auth system from the existing
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Rackspace architecture -- actually from a few existing auth systems -- and is
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therefore a bit disjointed. The distilled points about it are:
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* The authentication/authorization part can be an external system or a
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subsystem run within Swift as WSGI middleware
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* The user of Swift passes in an auth token with each request
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* Swift validates each token with the external auth system or auth subsystem
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and caches the result
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* The token does not change from request to request, but does expire
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The token can be passed into Swift using the X-Auth-Token or the
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X-Storage-Token header. Both have the same format: just a simple string
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representing the token. Some auth systems use UUID tokens, some an MD5 hash of
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something unique, some use "something else" but the salient point is that the
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token is a string which can be sent as-is back to the auth system for
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validation.
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Swift will make calls to the auth system, giving the auth token to be
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validated. For a valid token, the auth system responds with an overall
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expiration in seconds from now. Swift will cache the token up to the expiration
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time.
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The included TempAuth also has the concept of admin and non-admin users
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within an account. Admin users can do anything within the account.
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Non-admin users can only perform operations per container based on the
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container's X-Container-Read and X-Container-Write ACLs. Container ACLs
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use the "V1" ACL syntax, which looks like this:
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``name1, name2, .r:referrer1.com, .r:-bad.referrer1.com, .rlistings``
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For more information on ACLs, see :mod:`swift.common.middleware.acl`.
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Additionally, if the auth system sets the request environ's swift_owner key to
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True, the proxy will return additional header information in some requests,
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such as the X-Container-Sync-Key for a container GET or HEAD.
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In addition to container ACLs, TempAuth allows account-level ACLs. Any auth
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system may use the special header ``X-Account-Access-Control`` to specify
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account-level ACLs in a format specific to that auth system. (Following the
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TempAuth format is strongly recommended.) These headers are visible and
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settable only by account owners (those for whom ``swift_owner`` is true).
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Behavior of account ACLs is auth-system-dependent. In the case of TempAuth,
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if an authenticated user has membership in a group which is listed in the
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ACL, then the user is allowed the access level of that ACL.
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Account ACLs use the "V2" ACL syntax, which is a JSON dictionary with keys
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named "admin", "read-write", and "read-only". (Note the case sensitivity.)
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An example value for the ``X-Account-Access-Control`` header looks like this:
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``{"admin":["a","b"],"read-only":["c"]}`` Keys may be absent (as shown).
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The recommended way to generate ACL strings is as follows::
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from swift.common.middleware.acl import format_acl
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acl_data = { 'admin': ['alice'], 'read-write': ['bob', 'carol'] }
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acl_string = format_acl(version=2, acl_dict=acl_data)
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Using the :func:`format_acl` method will ensure
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that JSON is encoded as ASCII (using e.g. '\u1234' for Unicode). While
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it's permissible to manually send ``curl`` commands containing
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``X-Account-Access-Control`` headers, you should exercise caution when
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doing so, due to the potential for human error.
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Within the JSON dictionary stored in ``X-Account-Access-Control``, the keys
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have the following meanings:
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============ ==============================================================
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Access Level Description
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============ ==============================================================
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read-only These identities can read *everything* (except privileged
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headers) in the account. Specifically, a user with read-only
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account access can get a list of containers in the account,
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list the contents of any container, retrieve any object, and
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see the (non-privileged) headers of the account, any
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container, or any object.
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read-write These identities can read or write (or create) any container.
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A user with read-write account access can create new
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containers, set any unprivileged container headers, overwrite
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objects, delete containers, etc. A read-write user can NOT
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set account headers (or perform any PUT/POST/DELETE requests
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on the account).
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admin These identities have "swift_owner" privileges. A user with
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admin account access can do anything the account owner can,
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including setting account headers and any privileged headers
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-- and thus granting read-only, read-write, or admin access
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to other users.
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============ ==============================================================
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For more details, see :mod:`swift.common.middleware.tempauth`. For details
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on the ACL format, see :mod:`swift.common.middleware.acl`.
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Users with the special group ``.reseller_admin`` can operate on any account.
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For an example usage please see :mod:`swift.common.middleware.tempauth`.
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If a request is coming from a reseller the auth system sets the request environ
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reseller_request to True. This can be used by other middlewares.
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TempAuth will now allow OPTIONS requests to go through without a token.
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The user starts a session by sending a ReST request to the auth system to
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receive the auth token and a URL to the Swift system.
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-------------
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Keystone Auth
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-------------
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Swift is able to authenticate against OpenStack keystone via the
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:mod:`swift.common.middleware.keystoneauth` middleware.
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In order to use the ``keystoneauth`` middleware the ``authtoken``
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middleware from keystonemiddleware will need to be configured.
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The ``authtoken`` middleware performs the authentication token
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validation and retrieves actual user authentication information. It
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can be found in the keystonemiddleware distribution.
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The ``keystoneauth`` middleware performs authorization and mapping the
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``keystone`` roles to Swift's ACLs.
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Configuring Swift to use Keystone
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Configuring Swift to use Keystone is relatively straight
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forward. The first step is to ensure that you have the auth_token
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middleware installed, distributed with keystone it can either be
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dropped in your python path or installed via the keystone package.
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You need at first make sure you have a service endpoint of type
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``object-store`` in keystone pointing to your Swift proxy. For example
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having this in your ``/etc/keystone/default_catalog.templates`` ::
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catalog.RegionOne.object_store.name = Swift Service
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catalog.RegionOne.object_store.publicURL = http://swiftproxy:8080/v1/AUTH_$(tenant_id)s
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catalog.RegionOne.object_store.adminURL = http://swiftproxy:8080/
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catalog.RegionOne.object_store.internalURL = http://swiftproxy:8080/v1/AUTH_$(tenant_id)s
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On your Swift Proxy server you will want to adjust your main pipeline
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and add auth_token and keystoneauth in your
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``/etc/swift/proxy-server.conf`` like this ::
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[pipeline:main]
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pipeline = [....] authtoken keystoneauth proxy-logging proxy-server
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add the configuration for the authtoken middleware::
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[filter:authtoken]
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paste.filter_factory = keystonemiddleware.auth_token:filter_factory
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auth_host = keystonehost
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auth_port = 35357
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auth_protocol = http
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auth_uri = http://keystonehost:5000/
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admin_tenant_name = service
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admin_user = swift
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admin_password = password
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cache = swift.cache
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include_service_catalog = False
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The actual values for these variables will need to be set depending on
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your situation. For more information, please refer to the Keystone
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documentation on the ``auth_token`` middleware, but in short:
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* Those variables beginning with ``auth_`` point to the Keystone
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Admin service. This information is used by the middleware to actually
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query Keystone about the validity of the
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authentication tokens.
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* The admin auth credentials (``admin_user``, ``admin_tenant_name``,
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``admin_password``) will be used to retrieve an admin token. That
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token will be used to authorize user tokens behind the scenes.
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* cache is set to ``swift.cache``. This means that the middleware
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will get the Swift memcache from the request environment.
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* include_service_catalog defaults to True if not set. This means
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that when validating a token, the service catalog is retrieved
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and stored in the X-Service-Catalog header. Since Swift does not
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use the X-Service-Catalog header, there is no point in getting
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the service catalog. We recommend you set include_service_catalog
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to False.
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.. note::
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If support is required for unvalidated users (as with anonymous
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access) or for tempurl/formpost middleware, authtoken will need
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to be configured with delay_auth_decision set to 1.
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and you can finally add the keystoneauth configuration::
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[filter:keystoneauth]
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use = egg:swift#keystoneauth
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operator_roles = admin, swiftoperator
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By default the only users able to give ACL or to Create other
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containers are the ones who has the Keystone role specified in the
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``operator_roles`` setting.
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This user who have one of those role will be able to give ACLs to
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other users on containers, see the documentation on ACL here
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:mod:`swift.common.middleware.acl`.
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Users with the Keystone role defined in ``reseller_admin_role``
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(``ResellerAdmin`` by default) can operate on any account. The auth system
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sets the request environ reseller_request to True if a request is coming
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from a user with this role. This can be used by other middlewares.
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--------------
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Extending Auth
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--------------
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TempAuth is written as wsgi middleware, so implementing your own auth is as
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easy as writing new wsgi middleware, and plugging it in to the proxy server.
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The KeyStone project and the Swauth project are examples of additional auth
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services.
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Also, see :doc:`development_auth`.
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