keystone/doc/source/federation/configure_federation.rst

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, or by using Keystone as an Identity Provider (IdP).

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 14.04 and Apache 2.4.7.

To enable federation, you'll need to:

1. Run keystone under Apache, rather than using uwsgi command.
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:

• SAML - Keystone supports the following implementations:
  • Shibboleth - see Setup Shibboleth.
  • Mellon - see Setup Mellon.
• OpenID Connect - see Setup OpenID Connect.

Configure keystone and Horizon for Single Sign-On

• To configure horizon to access a federated keystone, follow the steps outlined at: Keystone Federation and Horizon.

Configure 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. Create keystone groups and assign roles
3. Add Identity Provider(s), Mapping(s), and Protocol(s)

Configure authentication drivers in keystone.conf

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.

For example, create a new domain and project like this:

$ openstack domain create federated_domain
$ openstack project create federated_project --domain federated_domain

And a new group like this:

$ openstack group create federated_users

Add the group to the domain and project:

$ openstack role add --group federated_users --domain federated_domain Member
$ openstack role add --group federated_users --project federated_project Member

We'll later add a mapping that makes all federated users a part of this group and therefore members of the new domain.

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

Read more about federation in keystone.

Identity Provider

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

$ openstack identity provider create --remote-id https://myidp.example.com/v3/OS-FEDERATION/saml2/idp myidp

The value for the remote-id option is the Entity ID provided by the IdP. It is the same value that you set for the SSO entityID in /etc/shibboleth/shibboleth2.xml. If the IdP is a Keystone IdP, it is the value set in that Keystone's [saml]/idp_entity_id option. It will usually appear as a URI but there is no requirement for it to resolve to anything and may be arbitrarily decided by the administrator of the IdP. The local name, here called 'myidp', is decided by you and will be used by the mapping and protocol, and later for authentication.

A keystone identity provider may have multiple remote_ids specified, this allows the same keystone identity provider resource to be used with multiple external identity providers. For example, an identity provider resource university-idp, may have the following `remote_ids`: ['university-x', 'university-y', 'university-z']. This removes the need to configure N identity providers in keystone.

Note

Remote IDs are globally unique. Two identity providers cannot be associated with the same remote ID. Once authenticated with the external identity provider, keystone will determine which identity provider and mapping to use based on the protocol and the value returned from the remote_id_attribute key.

For example, if our identity provider is google, the mapping used is google_mapping and the protocol is oidc. The identity provider's remote IDs would be: [accounts.google.com]. The remote_id_attribute value may be set to HTTP_OIDC_ISS, since this value will always be accounts.google.com.

The motivation for this approach is that there will always be some data sent by the identity provider (in the assertion or claim) that uniquely identifies the identity provider. This removes the requirement for horizon to list all the identity providers that are trusted by keystone.

Read more about identity providers.

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 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.

As a simple example, if keystone is your IdP, you can map a few known remote users to the group you already created:

$ cat > rules.json <<EOF
[
    {
        "local": [
            {
                "user": {
                    "name": "{0}"
                },
                "group": {
                    "domain": {
                        "name": "Default"
                    },
                    "name": "federated_users"
                }
            }
        ],
        "remote": [
            {
                "type": "openstack_user",
                "any_one_of": [
                    "demo",
                    "alt_demo"
                ]
            }
        ]
    }
]
EOF
$ openstack mapping create --rules rules.json myidp_mapping

As another example, if Shibboleth is your IdP, the remote section should use REMOTE_USER as the remote type:

$ cat > rules.json <<EOF
[
    {
        "local": [
            {
                "user": {
                    "name": "{0}"
                },
                "group": {
                    "domain": {
                        "name": "Default"
                    },
                    "name": "federated_users"
                }
            }
        ],
        "remote": [
            {
                "type": "REMOTE_USER"
            }
        ]
    }
]
EOF
$ openstack mapping create --rules rules.json myidp_mapping

Read more about mapping.

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.

You can create a protocol like this:

$ openstack federation protocol create mapped --mapping myidp_mapping --identity-provider myidp

The name you give the protocol is not arbitrary. It must match the method name you gave in the [auth]/methods config option. When authenticating it will be referred to as the protocol_id.

Read more about federation protocols

Performing federated authentication

Note

Authentication with keystone-to-keystone federation does not follow these steps. See Testing it all out to authenticate with keystone-to-keystone.

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 JSON format, with the ID in the X-Subject-Token header.

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

Read more about getting an unscoped token.

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

Read more about listing resources.

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.

Read more about getting a scoped token.

Example cURL

$ curl -X POST -H "Content-Type: application/json" -d '{"auth":{"identity":{"methods":["mapped"],"mapped":{"id":"<unscoped_token_id>"}},"scope":{"project":{"domain": {"name": "federated_domain"},"name":"federated_project"}}}}' -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]
idp_entity_id=https://myidp.example.com/v3/OS-FEDERATION/saml2/idp
idp_sso_endpoint=https://myidp.example.com/v3/OS-FEDERATION/saml2/sso

idp_entity_id is the unique identifier for the Identity Provider. It usually takes the form of a URI but it does not have to resolve to anything. idp_sso_endpoint is required to generate valid metadata but its value is not important, though it may be in the future.

Note the certfile, keyfile, and idp_metadata_path settings and adjust them if necessary:

certfile=/etc/keystone/ssl/certs/signing_cert.pem
keyfile=/etc/keystone/ssl/private/signing_key.pem
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=555-555-5555
idp_contact_type=technical

Generate Metadata

In order to create a trust between the IdP and SP, metadata must be exchanged.

First, if you haven't already generated a PKI key pair, you need to do so and copy those files the locations designated by certfile and keyfile options that were assigned in the previous section. Ensure that your apache vhost has SSL enabled and is using that keypair by adding the following to the vhost:

SSLEngine on
SSLCertificateFile /etc/keystone/ssl/certs/signing_cert.pem
SSLCertificateKeyFile /etc/keystone/ssl/private/signing_key.pem

To create metadata for your keystone IdP, run the keystone-manage command and redirect 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.

Finally, restart apache.

Create a Service Provider (SP)

In this example we are creating a new Service Provider with an ID of mysp, a sp_url of http://mysp.example.com/Shibboleth.sso/SAML2/ECP and a auth_url of http://mysp.example.com:5000/v3/OS-FEDERATION/identity_providers/myidp/protocols/mapped/auth . The sp_url will be used when creating a SAML assertion for mysp and signed by the current keystone IdP. The auth_url is used to retrieve the token for mysp once the SAML assertion is sent. The auth_url has the format described in Get an unscoped token.

$ openstack service provider create --service-provider-url 'http://mysp.example.com/Shibboleth.sso/SAML2/ECP' --auth-url http://mysp.example.com:5000/v3/OS-FEDERATION/identity_providers/myidp/protocols/mapped/auth mysp

Testing it all out

Use keystoneauth to create a password session with the IdP, then use the session to authenticate with the SP, and get a scoped token from the SP.

Note

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

import os

from keystoneauth1 import session
from keystoneauth1.identity import v3
from keystoneauth1.identity.v3 import k2k

auth = v3.Password(auth_url=os.environ.get('OS_AUTH_URL'),
                   username=os.environ.get('OS_USERNAME'),
                   password=os.environ.get('OS_PASSWORD'),
                   user_domain_name=os.environ.get('OS_USER_DOMAIN_NAME'),
                   project_name=os.environ.get('OS_PROJECT_NAME'),
                   project_domain_name=os.environ.get('OS_PROJECT_DOMAIN_NAME'))
password_session = session.Session(auth=auth)
k2ksession = k2k.Keystone2Keystone(password_session.auth, 'mysp',
                                   domain_name='federated_domain')
auth_ref = k2ksession.get_auth_ref(password_session)
scoped_token_id = auth_ref.auth_token
print('Scoped token id: %s' % scoped_token_id)