The Auth System¶
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:
It is also possible to write your own auth system as described in Extending Auth.
TempAuth is used primarily in Swift’s functional test environment and can be used in other test environments (such as SAIO - Swift All In One). 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
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
X-Container-Writemetadata. See Container ACLs for more information.
- Per account ACLs based on the account’s
X-Account-Access-Controlmetadata. For more information see 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.
Swift is able to authenticate against OpenStack Keystone. In this environment, Keystone is responsible for creating and validating tokens. The KeystoneAuth middleware is responsible for implementing the auth system within Swift as described here.
The account-level ACL is not supported by Keystone auth.
In order to use the
keystoneauth middleware the
middleware from KeystoneMiddleware will need to be configured.
authtoken middleware performs the authentication token
validation and retrieves actual user authentication information. It
can be found in the KeystoneMiddleware distribution.
The KeystoneAuth middleware performs authorization and mapping the Keystone roles to Swift’s ACLs.
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
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
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 auth_uri = http://keystonehost:5000/ auth_url = http://keystonehost:35357/ 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:
auth_urishould 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_urlpoints 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 (
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 for other examples.
cacheis set to
swift.cache. This means that the middleware will get the Swift memcache from the request environment.
Trueif not set. This means that when validating a token, the service catalog is retrieved and stored in the
X-Service-Catalogheader. Since Swift does not use the
X-Service-Catalogheader, there is no point in getting the service catalog. We recommend you set
The authtoken config variable
delay_auth_decision must be set to
True. The default is
False, but that breaks public access,
StaticWeb, FormPost, TempURL, and authenticated
capabilities requests (using 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 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
[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
/etc/keystone/default_catalog.templatesabove). Normally this is
- The second item in the reseller_prefix list is the prefix used by the
OpenStack services(s). You must configure this value (
SERVICEin 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
serviceis 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
- 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
swiftoperatorrole(s). When validated, the service token gives the
- 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
servicerole as described by the
- 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
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
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
respectively. In addition to the ACL formats described
here, keystoneauth supports ACLs using the
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
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.
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 KeystoneAuth
Users with the Keystone role defined in
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. 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
authtokenmiddleware options in the Swift proxy server.
authtokenmiddleware communicates with the Keystone service to validate tokens that are presented with client requests. To do this
authtokenmust authenticate itself with Keystone using the credentials configured in the
/etc/swift/proxy-server.conf. Errors in these credentials can result in
authtokenfailing to validate tokens and may be revealed in the proxy server logs by a message such as:
proxy-server: Identity server rejected authorization
More detailed log messaging may be seen by setting the
log_level = debug.
authtokenconfiguration options may be checked by attempting to use them to communicate directly with Keystone using an
openstackcommand line. For example, given the
authtokenconfiguration sample shown in Configuring Swift to use Keystone, 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
openstackcommand fails then it is likely that there is a problem with the
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. The Swauth project is an example of an additional auth service.
See Auth Server and Middleware for detailed information on extending the auth system.