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Glance Authentication With Keystone

Glance may optionally be integrated with Keystone. Setting this up is relatively straightforward, as the Keystone distribution includes the necessary middleware. Once you have installed Keystone and edited your configuration files, newly created images will have their owner attribute set to the tenant of the authenticated users, and the is_public attribute will cause access to those images for which it is false to be restricted to only the owner.

Note

The exception is those images for which owner is set to null, which may only be done by those users having the Admin role. These images may still be accessed by the public, but will not appear in the list of public images. This allows the Glance Registry owner to publish images for beta testing without allowing those images to show up in lists, potentially confusing users.

Configuring the Glance servers to use Keystone

Keystone is integrated with Glance through the use of middleware. The default configuration files for both the Glance API and the Glance Registry use a single piece of middleware called context, which generates a request context without any knowledge of Keystone. In order to configure Glance to use Keystone, this context middleware must be replaced with two other pieces of middleware: the authtoken middleware and the auth-context middleware, both of which may be found in the Keystone distribution. The authtoken middleware performs the Keystone token validation, which is the heart of Keystone authentication. On the other hand, the auth-context middleware performs the necessary tie-in between Keystone and Glance; it is the component which replaces the context middleware that Glance uses by default.

One other important concept to keep in mind is the request context. In the default Glance configuration, the context middleware sets up a basic request context; configuring Glance to use auth_context causes a more advanced context to be configured. It is also important to note that the Glance API and the Glance Registry use two different context classes; this is because the registry needs advanced methods that are not available in the default context class. The implications of this will be obvious in the below example for configuring the Glance Registry.

Configuring Glance API to use Keystone

Configuring Glance API to use Keystone is relatively straight forward. The first step is to ensure that declarations for the two pieces of middleware exist in the glance-api-paste.ini. Here is an example for authtoken:

[filter:authtoken]
paste.filter_factory = keystone.middleware.auth_token:filter_factory
service_protocol = http
service_host = 127.0.0.1
service_port = 5000
auth_host = 127.0.0.1
auth_port = 35357
auth_protocol = http
auth_uri = http://127.0.0.1:5000/
admin_token = 999888777666
admin_user = glance_admin
admin_tenant_name = service_admins
admin_password = password1234

The actual values for these variables will need to be set depending on your situation. For more information, please refer to the Keystone documentation on the auth_token middleware, but in short:

  • Those variables beginning with service_ are only needed if you are using a proxy; they define the actual location of Glance. That said, they must be present.
  • Except for auth_uri, those variables beginning with auth_ point to the Keystone Admin service. This information is used by the middleware to actually query Keystone about the validity of the authentication tokens.
  • The auth_uri variable must point to the Keystone Auth service, which is the service users use to obtain Keystone tokens. If the user does not have a valid Keystone token, they will be redirected to this URI to obtain one.
  • The admin_token variable specifies the administrative token that Glance uses in its query to the Keystone Admin service.
  • If no admin_token is provided, or it becomes invalid, the admin auth credentials (admin_user, admin_tenant_name, admin_password) will be used to retrieve a new admin token

The other piece of middleware needed for Glance API is the auth-context:

[filter:auth_context]
paste.filter_factory = glance.common.wsgi:filter_factory
glance.filter_factory = keystone.middleware.glance_auth_token:KeystoneContextMiddleware

Finally, to actually enable using Keystone authentication, the application pipeline must be modified. By default, it looks like:

[pipeline:glance-api]
pipeline = versionnegotiation context apiv1app

(Your particular pipeline may vary depending on other options, such as the image cache.) This must be changed by replacing context with authtoken and auth-context:

[pipeline:glance-api]
pipeline = versionnegotiation authtoken auth-context apiv1app

Configuring Glance Registry to use Keystone

Configuring Glance Registry to use Keystone is also relatively straight forward. The same pieces of middleware need to be added to glance-registry-paste.ini as are needed by Glance API; see above for an example of the authtoken configuration. There is a slight difference for the auth-context middleware, which should look like this:

[filter:auth-context]
context_class = glance.registry.context.RequestContext
paste.filter_factory = glance.common.wsgi:filter_factory
glance.filter_factory = keystone.middleware.glance_auth_token:KeystoneContextMiddleware

The context_class variable is needed to specify the Registry-specific request context, which contains the extra access checks used by the Registry.

Again, to enable using Keystone authentication, the appropriate application pipeline must be selected. By default, it looks like:

[pipeline:glance-registry-keystone] pipeline = authtoken auth-context registryapp

To enable the above application pipeline, in your main glance-registry.conf configuration file, select the appropriate deployment flavor by adding a flavor attribute in the paste_deploy group:

[paste_deploy]
flavor = keystone

Sharing Images With Others

It is possible to allow a private image to be shared with one or more alternate tenants. This is done through image memberships, which are available via the members resource of images. (For more details, see glanceapi.) Essentially, a membership is an association between an image and a tenant which has permission to access that image. These membership associations may also have a can_share attribute, which, if set to true, delegates the authority to share an image to the named tenant.

Configuring the Glance Client to use Keystone

Once the Glance API and Registry servers have been configured to use Keystone, you will need to configure the Glance client (bin/glance) to use Keystone as well. Like the other OpenStack projects, this is done through a common set of environment variables. These credentials may may alternatively be specified using the following switches to the bin/glance command:

OS_USERNAME=<USERNAME>, -I <USERNAME>, --os_username=<USERNAME>

User name used to acquire an authentication token

OS_PASSWORD=<PASSWORD>, -K <PASSWORD>, --os_password=<PASSWORD>

Password used to acquire an authentication token

OS_TENANT_NAME=<TENANT_NAME> -T <TENANT_NAME>, --os_tenant_name=<TENANT_NAME>

Tenant name

OS_AUTH_URL=<AUTH_URL>, -N <AUTH_URL>, --os_auth_url=<AUTH_URL>

Authentication endpoint

OS_REGION_NAME=<REGION_NAME>, -R <REGION_NAME>, --os_region_name=<REGION_NAME>

Used to select a specific region while authenticating against Keystone

Or, if a pre-authenticated token is preferred, the following option allows the client-side interaction with keystone to be bypassed (useful if a long sequence of commands is being scripted):

OS_TOKEN=<TOKEN>, -A <TOKEN>, --os_auth_token=<TOKEN>

User's authentication token that identifies the client to the glance server. This is not an admin token.

In general the command line switch takes precedence over the corresponding OS* environment variable, if both are set.