Configuring Keystone for Federation

Definitions

  • Service Provider (SP): provides a service to an end-user.
  • Identity Provider (IdP): service that stores information about users and groups.
  • SAML assertion: contains information about a user as provided by an IdP.

Keystone as a Service Provider (SP)

Note

This feature is considered stable and supported as of the Juno release.

Prerequisites

This approach to federation supports keystone as a Service Provider, consuming identity properties issued by an external Identity Provider, such as SAML assertions or OpenID Connect claims.

Federated users are not mirrored in the keystone identity backend (for example, using the SQL driver). The external Identity Provider is responsible for authenticating users, and communicates the result of authentication to keystone using identity properties. Keystone maps these values to keystone user groups and assignments created in keystone.

The following configuration steps were performed on a machine running Ubuntu 12.04 and Apache 2.2.22.

To enable federation, you’ll need to:

  1. Run keystone under Apache, rather than using keystone-all.
  2. Configure Apache to use a federation capable authentication method.
  3. Configure federation in keystone.

Configure Apache to use a federation capable authentication method

There is currently support for two major federation protocols:

Configure keystone and Horizon for Single Sign-On

Configuring Federation in Keystone

Now that the Identity Provider and keystone are communicating we can start to configure federation.

  1. Configure authentication drivers in keystone.conf
  2. Add local keystone groups and roles
  3. Add Identity Provider(s), Mapping(s), and Protocol(s)

Configure authentication drivers in keystone.conf

Note

saml2 has been deprecated as of the Mitaka release. Support for the saml2 wrapper will be removed as of the “O” release. The recommended authentication method is mapped, which supports saml2.

Add the authentication methods to the [auth] section in keystone.conf. Names should be equal to protocol names added via Identity API v3. Here we use examples mapped and openid.

[auth]
methods = external,password,token,mapped,openid

Create keystone groups and assign roles

As mentioned earlier, no new users will be added to the Identity backend, but the Identity Service requires group-based role assignments to authorize federated users. The federation mapping function will map the user into local Identity Service groups objects, and hence to local role assignments.

Thus, it is required to create the necessary Identity Service groups that correspond to the Identity Provider’s groups; additionally, these groups should be assigned roles on one or more projects or domains.

You may be interested in more information on group management and role assignments, both of which are exposed to the CLI via python-openstackclient.

Add Identity Provider(s), Mapping(s), and Protocol(s)

To utilize federation the following must be created in the Identity Service:

  • Identity Provider
  • Mapping
  • Protocol

More information on federation in keystone can be found here.

Identity Provider

Create an Identity Provider object in keystone, which represents the Identity Provider we will use to authenticate end users.

More information on identity providers can be found here.

Mapping

A mapping is a list of rules. The only Identity API objects that will support mapping are groups and users.

Mapping adds a set of rules to map federation protocol attributes to Identity API objects. There are many different ways to setup as well as combine these rules. More information on rules can be found on the Mapping Combinations for Federation page.

An Identity Provider has exactly one mapping specified per protocol. Mapping objects can be used multiple times by different combinations of Identity Provider and Protocol.

More information on mapping can be found here.

Protocol

A protocol contains information that dictates which Mapping rules to use for an incoming request made by an IdP. An IdP may have multiple supported protocols.

Add Protocol object and specify the mapping id you want to use with the combination of the IdP and Protocol.

Performing federated authentication

  1. Authenticate externally and generate an unscoped token in keystone
  2. Determine accessible resources
  3. Get a scoped token

Get an unscoped token

Unlike other authentication methods in the Identity Service, the user does not issue an HTTP POST request with authentication data in the request body. To start federated authentication a user must access the dedicated URL with Identity Provider’s and Protocol’s identifiers stored within a protected URL. The URL has a format of: /v3/OS-FEDERATION/identity_providers/{idp_id}/protocols/{protocol_id}/auth.

In this instance we follow a standard SAML2 authentication procedure, that is, the user will be redirected to the Identity Provider’s authentication webpage and be prompted for credentials. After successfully authenticating the user will be redirected to the Service Provider’s endpoint. If using a web browser, a token will be returned in XML format.

In the returned unscoped token, a list of Identity Service groups the user belongs to will be included.

More information on getting an unscoped token can be found here.

Example cURL

Note that the request does not include a body. The following url would be considered protected by mod_shib and Apache, as such a request made to the URL would be redirected to the Identity Provider, to start the SAML authentication procedure.

$ curl -X GET -D - http://localhost:5000/v3/OS-FEDERATION/identity_providers/{idp_id}/protocols/{protocol_id}/auth

Determine accessible resources

By using the previously returned token, the user can issue requests to the list projects and domains that are accessible.

  • List projects a federated user can access: GET /OS-FEDERATION/projects
  • List domains a federated user can access: GET /OS-FEDERATION/domains

More information on listing resources can be found here.

Example cURL
$ curl -X GET -H "X-Auth-Token: <unscoped token>" http://localhost:5000/v3/OS-FEDERATION/projects

or

$ curl -X GET -H "X-Auth-Token: <unscoped token>" http://localhost:5000/v3/OS-FEDERATION/domains

Get a scoped token

A federated user may request a scoped token, by using the unscoped token. A project or domain may be specified by either id or name. An id is sufficient to uniquely identify a project or domain.

More information on getting a scoped token can be found here.

Example cURL
$ curl -X POST -H "Content-Type: application/json" -d '{"auth":{"identity":{"methods":["mapped"],"saml2":{"id":"<unscoped_token_id>"}},"scope":{"project":{"domain": {"name": "Default"},"name":"service"}}}}' -D - http://localhost:5000/v3/auth/tokens

Keystone as an Identity Provider (IdP)

Note

This feature is experimental and unsupported in Juno (with several issues that will not be backported). These issues have been fixed and this feature is considered stable and supported as of the Kilo release.

Note

This feature requires installation of the xmlsec1 tool via your distribution packaging system (for instance apt or yum)

Example for apt:

$ apt-get install xmlsec1

Configuration Options

There are certain settings in keystone.conf that must be setup, prior to attempting to federate multiple keystone deployments.

Within keystone.conf, assign values to the [saml] related fields, for example:

[saml]
certfile=/etc/keystone/ssl/certs/ca.pem
keyfile=/etc/keystone/ssl/private/cakey.pem
idp_entity_id=https://keystone.example.com/v3/OS-FEDERATION/saml2/idp
idp_sso_endpoint=https://keystone.example.com/v3/OS-FEDERATION/saml2/sso
idp_metadata_path=/etc/keystone/saml2_idp_metadata.xml

Though not necessary, the follow Organization configuration options should also be setup. It is recommended that these values be URL safe.

idp_organization_name=example_company
idp_organization_display_name=Example Corp.
idp_organization_url=example.com

As with the Organization options, the Contact options, are not necessary, but it’s advisable to set these values too.

idp_contact_company=example_company
idp_contact_name=John
idp_contact_surname=Smith
idp_contact_email=jsmith@example.com
idp_contact_telephone=555-55-5555
idp_contact_type=technical

Generate Metadata

In order to create a trust between the IdP and SP, metadata must be exchanged. To create metadata for your keystone IdP, run the keystone-manage command and pipe the output to a file. For example:

$ keystone-manage saml_idp_metadata > /etc/keystone/saml2_idp_metadata.xml

Note

The file location should match the value of the configuration option idp_metadata_path that was assigned in the previous section.

Create a Service Provider (SP)

In this example we are creating a new Service Provider with an ID of BETA, a sp_url of http://beta.example.com/Shibboleth.sso/SAML2/ECP and a auth_url of http://beta.example.com:5000/v3/OS-FEDERATION/identity_providers/beta/protocols/saml2/auth . The sp_url will be used when creating a SAML assertion for BETA and signed by the current keystone IdP. The auth_url is used to retrieve the token for BETA once the SAML assertion is sent. Although the enabled field is optional we are passing it set to true otherwise it will be set to false by default.

$ curl -s -X PUT \
  -H "X-Auth-Token: $OS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"service_provider": {"auth_url": "http://beta.example.com:5000/v3/OS-FEDERATION/identity_providers/beta/protocols/saml2/auth", "sp_url": "https://example.com:5000/Shibboleth.sso/SAML2/ECP", "enabled": true}}' \
  http://localhost:5000/v3/OS-FEDERATION/service_providers/BETA | python -mjson.tool

Testing it all out

Lastly, if a scoped token and a Service Provider scope are presented to the local keystone, the result will be a full ECP wrapped SAML Assertion, specifically intended for the Service Provider keystone.

Note

ECP stands for Enhanced Client or Proxy, an extension from the SAML2 protocol used in non-browser interfaces, like in the following example with cURL.

$ curl -s -X POST \
  -H "Content-Type: application/json" \
  -d '{"auth": {"scope": {"service_provider": {"id": "BETA"}}, "identity": {"token": {"id": "d793d935b9c343f783955cf39ee7dc3c"}, "methods": ["token"]}}}' \
  http://localhost:5000/v3/auth/OS-FEDERATION/saml2/ecp

Note

Use URL http://localhost:5000/v3/auth/OS-FEDERATION/saml2 to request for pure SAML Assertions.

At this point the ECP wrapped SAML Assertion can be sent to the Service Provider keystone using the provided auth_url in the X-Auth-Url header present in the response containing the Assertion, and a valid OpenStack token, issued by a Service Provider keystone, will be returned.