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Keystone-to-Keystone federation with the openstack-ansible project

Federation support in OpenStack has been greatly improved in the Kilo release, and, while there are still some rough edges, the feature is now usable, if you don’t mind adding a little elbow grease. This article focuses on one specific configuration called Keystone-to-Keystone federation (or K2K), in which users of an OpenStack cloud use their credentials to access services in another OpenStack cloud, with both clouds using Keystone as their identity services.

The purpose of this article is twofold. First, I want to show you how to configure K2K federation between two openstack-ansible clouds. Then, I want to touch on some of those rough edges I mentioned above, so that you have your expectations set at the right level.

What is OpenStack federation?

In a standard, non-federated set up, users authenticate against the cloud’s own identity APIs, usually implemented by the Keystone service. With Keystone federation, the options for authentication are expanded by creating a separation between the entity that authenticates the user (the identity provider, or IdP) and the entity that owns the cloud resources the user wants to access (the service provider, or SP).

Since we are talking about OpenStack, it is obvious that the service provider in all the federation use cases is an OpenStack cloud. But on the IdP side things are more interesting, because it is now possible to use a variety of external identity services, such as those based on ADFS, OpenID Connect or SAML2. As a result, an external IdP service that has a trust relationship with the SP cloud can offer access to resources in the SP cloud to all of its users, without those users needing explicit SP cloud accounts.

What is Keystone-to-Keystone federation?

When you have an OpenStack cloud acting as IdP to another OpenStack cloud, you have K2K federation. In this situation, the Keystone service in the SP cloud is configured to trust the Keystone service in the IdP cloud with user authentication, so any users of the IdP cloud can access resources of the SP cloud as if they had a local account.

There are many useful workflows that are made possible by K2K federation. Consider a company that operates in multiple regions, each with its own regional cloud. With K2K, the users in one region can automatically access the clouds in the other regions when they need to. Another interesting application is the creation of a hybrid private/public cloud. Imagine a company that has an on-premise private cloud that can dynamically expand to a much larger public cloud when its local resources are all in use.

What is the openstack-ansible project?

The openstack-ansible project is an open source initiative from Rackspace that provides Ansible playbooks to deploy production-ready OpenStack private clouds of any size, directly from the official OpenStack repositories and without any vendor-specific additions. Note that this project was originally hosted on stackforge with the name os-ansible-deployment.

One of the strong selling points of this project, and one that distinguishes it from other OpenStack distributions, is that the OpenStack services are installed in individual LXC containers, so they are isolated from each other. Configuration options are given in YAML files, which are simple, hierarchical text files that can be edited in your favorite text editor. The Ansible model simplifies the management of the OpenStack cluster, so that for example, adding a new compute node to an existing cloud just requires editing the configuration file that lists all the nodes, and then re-running the playbooks. Each time you run the playbooks, Ansible detects what changed in the configuration files, and invokes the appropriate tasks to update the cluster accordingly with minimal or no disruption to the cluster. If one of the services starts to misbehave, just delete its container and run the Ansible playbooks to create a brand new container to take the place of the bad one. It’s that simple.

Deploying an openstack-ansible all-in-one

Describing the openstack-ansible configuration in detail is outside the scope of this article, but I want to quickly show you how you can do a single-node install that is appropriate for testing and evaluation, in case you are interested in actually playing with K2K federation instead of just reading about it from me.

The openstack-ansible project is based on Ubuntu 14.04, so you need to install this operating system to prepare a host for the deployment. I have found that a host with 8GB of RAM and 60GGB of disk space is enough to host an all-in-one installation. A very good option for a single-node deployment is to use a public cloud server. If you have access to the Rackspace public cloud, a node that uses the performance1-8 flavor is a good choice.

The only package that you need to have installed in your host to be able to launch an install is git:

# apt-get install git

With it, you have to clone the kilo branch of the openstack-ansible repository:

# git clone -b kilo /opt/openstack-ansible

Luckily, the project includes scripts that simplify single-node deployments, which we use for development work and gate checks. These scripts take care of all the configuration and setup appropriate for an all-in-one, so all that you need to do is run the following scripts:

# cd /opt/openstack-ansible
# scripts/
# scripts/
# scripts/

Now you can go grab a cup of coffee (or three), and let Ansible install OpenStack for you. The process normally takes about 45 minutes to one hour to complete.

Once the install finishes, your OpenStack cloud is ready to be used. Horizon is accessible on the public IP address of your server. If you haven’t changed the default configuration, then the username is admin and the password is randomly generated and different every time. The configuration files for the installation can be found in the /etc/openstack_deploy directory. To find your admin password, you can run the following command:

# grep keystone_auth_admin_password /etc/openstack_deploy/user_secrets.yml

Remember that I mentioned that the openstack services are deployed to LXC containers? You can use the lxc-ls command to list the containers in your installation:

# lxc-ls -f
NAME                                          STATE    IPV4                                       IPV6  AUTOSTART
aio1_ceilometer_api_container-0156d950        RUNNING,                 -     YES (onboot, openstack)
aio1_ceilometer_collector_container-bb0887dd  RUNNING,                 -     YES (onboot, openstack)
aio1_cinder_api_container-6f4f639d            RUNNING,,  -     YES (onboot, openstack)
aio1_cinder_scheduler_container-ec7a787a      RUNNING,                  -     YES (onboot, openstack)
aio1_galera_container-752f369f                RUNNING,                 -     YES (onboot, openstack)
aio1_galera_container-9d4079b5                RUNNING,                  -     YES (onboot, openstack)
aio1_galera_container-f7aa239a                RUNNING,                   -     YES (onboot, openstack)
aio1_glance_container-7da663ca                RUNNING,,  -     YES (onboot, openstack)
aio1_heat_apis_container-6049fd20             RUNNING,                   -     YES (onboot, openstack)
aio1_heat_engine_container-fbfba3d3           RUNNING,                  -     YES (onboot, openstack)
aio1_horizon_container-9f338a14               RUNNING,                  -     YES (onboot, openstack)
aio1_horizon_container-af801068               RUNNING,                  -     YES (onboot, openstack)
aio1_keystone_container-67b7e278              RUNNING,                  -     YES (onboot, openstack)
aio1_keystone_container-83926b44              RUNNING,                  -     YES (onboot, openstack)
aio1_memcached_container-939aa985             RUNNING,                    -     YES (onboot, openstack)
aio1_neutron_agents_container-41c766fa        RUNNING,,  -     YES (onboot, openstack)
aio1_neutron_server_container-7f869c25        RUNNING,                 -     YES (onboot, openstack)
aio1_nova_api_metadata_container-0f0c95ac     RUNNING,                 -     YES (onboot, openstack)
aio1_nova_api_os_compute_container-10b4cc35   RUNNING,                 -     YES (onboot, openstack)
aio1_nova_cert_container-dc9f80e1             RUNNING,                  -     YES (onboot, openstack)
aio1_nova_conductor_container-3f4681b9        RUNNING,                  -     YES (onboot, openstack)
aio1_nova_console_container-58618b58          RUNNING,                 -     YES (onboot, openstack)
aio1_nova_scheduler_container-3d1b4e9d        RUNNING,                 -     YES (onboot, openstack)
aio1_rabbit_mq_container-0f3542d2             RUNNING,                 -     YES (onboot, openstack)
aio1_rabbit_mq_container-4dc00e4c             RUNNING,                   -     YES (onboot, openstack)
aio1_rabbit_mq_container-cea24e2c             RUNNING,                   -     YES (onboot, openstack)
aio1_repo_container-4cf3b996                  RUNNING,                 -     YES (onboot, openstack)
aio1_repo_container-6511c33a                  RUNNING,                   -     YES (onboot, openstack)
aio1_rsyslog_container-dbae4650               RUNNING,                  -     YES (onboot, openstack)
aio1_swift_proxy_container-0f90e545           RUNNING,,  -     YES (onboot, openstack)
aio1_utility_container-d7a0a0e0               RUNNING,                  -     YES (onboot, openstack)

The first interesting thing you may notice is that even though this is a single-node deployment, the use of containers makes it possible to deploy redundant services. You can see in the above listing that keystone, rabbitmq, galera and a few others are deployed in multiple containers. The set up script installs haproxy as a load balancer for these.

Among all the containers, you’ll find one with the name utility, usually at the bottom of the list. This container has all the OpenStack command line clients installed, and is appropriate for accessing the cloud from the command line. Below you can see an example session in which I use the openstack command line utility to query the list of users:

# ssh aio1_utility_container-d7a0a0e0
Welcome to Ubuntu 14.04.3 LTS (GNU/Linux 3.13.0-58-generic x86_64)
Last login: Wed Sep  2 21:31:34 2015 from
root@aio1_utility_container-d7a0a0e0:~# source openrc
root@aio1_utility_container-d7a0a0e0:~# openstack user list
| ID                               | Name                           |
| 0ce7c8c8d75c44c38e52fe4414482aff | cinder                         |
| 12ca8c329fdd48f7a7fdc69ec8153962 | demo                           |
| 28d0e28f46fd446195b9eaedbe1085aa | swift                          |
| 346498bb40a741d48df728d6a5fd1eef | stack_domain_admin             |
| 595b2db82173460a994d23b29967a207 | glance                         |
| 5fa7bf9a79aa4782b5657bd23d95082c | heat                           |
| 8eb91912e1e2466ab781b317c358c109 | neutron                        |
| 925e531fdbf340bbbcd0825d9c6f94f1 | keystone                       |
| af7ecc9999c44e6e8459ddc3810e128d | ceilometer                     |
| c9c2e4e7fa264c10809121ffda2a9d14 | admin                          |
| fedf070e403343d18fadb04dbc063048 | nova                           |

In the following sections, I will describe how to connect two openstack-ansible installations through K2K federation.

K2K configuration for openstack-ansible

As an OpenStack deployer, one of the nicest aspects of the openstack-ansible project is the ease of introducing configuration changes. In the Ansible model, all the tasks that make up a deployment are idempotent, so that they can be executed multiple times without causing problems. So effectively, every time you run the playbooks, Ansible can easily apply changes given in the configuration files, while all the things that did not change from the previous run are unaffected.

Specifically for K2K federation, this means that connecting two existing OpenStack clouds requires very little work, and a minimal disruption to the Keystone services (a second or two that it takes to restart the services after the configuration changes are applied).

If you are going to follow along and set up your own K2K federation test, then at this point it would be a good idea that you deploy the two clouds that you will use. You can follow the instructions from the previous section to stand up two single-node clouds. Before you continue, verify that you can access both clouds through their utility containers, as shown above.

Setting up the IdP cloud

To configure an openstack-ansible install as an identity provider for federation, the IdP configuration must be added. A good place to write this configuration is in the /etc/openstack_deploy/user_variables.yml file. Note that any files in the /etc/openstack_deploy directory that match the user_*.yml pattern are imported by the Ansible playbooks, so if you want, you can also write it in a brand new file, as long as it matches the pattern.

The IdP configuration is shown below:

keystone_idp_id: my_idp
keystone_sp_id: my_sp

    - id: "{{ "{{ " }}keystone_sp_id{{ " }}" }}"
      auth_url: https://{{ "{{ " }}keystone_sp_host{{ " }}" }}:5000/v3/OS-FEDERATION/identity_providers/{{ "{{ " }}keystone_idp_id{{ " }}" }}/protocols/saml2/auth
      sp_url: https://{{ "{{ " }}keystone_sp_host{{ " }}" }}:5000/Shibboleth.sso/SAML2/ECP
  idp_entity_id: "{{ "{{ " }}keystone_service_publicurl_v3{{ " }}" }}/OS-FEDERATION/saml2/idp"
  idp_sso_endpoint: "{{ "{{ " }}keystone_service_publicurl_v3{{ " }}" }}/OS-FEDERATION/saml2/sso"
  idp_metadata_path: /etc/keystone/saml2_idp_metadata.xml
  certfile: "/etc/keystone/ssl/idp_signing_cert.pem"
  keyfile: "/etc/keystone/ssl/idp_signing_key.pem"
  self_signed_cert_subject: "/C=US/ST=Texas/L=San Antonio/O=IT/CN={{ "{{ " }}external_lb_vip_address{{ " }}" }}"
  regen_cert: false

keystone_token_provider: "keystone.token.providers.uuid.Provider"
keystone_token_driver: "keystone.token.persistence.backends.sql.Token"

You can see at the top of the above snippet that I have defined three top-level variables. The first two hold user-defined unique identifiers for the IdP and SP clouds. The third variable defines the public IP address or hostname of the SP cloud. These are custom variables that I intend to use later. Since this is an Ansible configuration file, these variables can be referenced in other variables with the {{ "{{ " }}variable_name{{ " }}" }} syntax.

The block of variables that configure the cloud as an IdP is defined inside the keystone_idp root element. The most important setting in this block is the reference to the SP cloud, which is given in the service_providers variable. For each service provider, three configuration items must be provided: the provider’s unique identifier, its auth_url, and its sp_url. Note how the id is generated using the keystone_sp_id custom variable that I defined above. For the other two variables Keystone has predefined URLs, so the only thing that changes from one install to the next is the SP cloud’s public IP address or hostname, which again, I replace from one of my custom variables at the top.

I should note that the service_providers variable contains a list, which means that you can attach more than one service provider cloud. When using multiple SPs, it is required that each SP cloud is configured with a unique identifier.

The remaining variables under keystone_idp can normally be set identically in all installs. Among these settings there are a few that configure the SSL certificate that is used by the SAML2 protocol, which is automatically generated as part of the install. Out of all these variables, the regen_cert variable deserves a mention. This variable can be used to force Ansible to replace an existing certificate with a new one, simply by setting the variable to true. If this variable is set to false, then repeated runs of the playbook will leave the same certificate installed.

The last two variables configure Keystone to use UUID tokens. At this time, this is required in the Kilo branch. The openstack-ansible project configures Keystone to use Fernet tokens by default, but there are currently issues with this token provider and federation. Once the Fernet token fixes are backported these two lines can be omitted.

Are you ready to convert one of your two test clouds to an identity provider? Just add the above snippet to /etc/openstack_deploy/user_variables.yml, and make sure you write the IP address or hostname of your other cloud in the keystone_sp_host variable. To make this configuration change effective, you just simply need to run the playbooks again. Since this change only affects keystone, we will just run the keystone playbook to save a bit of time:

# cd /opt/openstack-ansible/playbooks
# openstack-ansible os-keystone-install.yml

Ansible will now run for a few minutes, and, when the playbook completes, your first cloud will be configured as an identity provider. Pretty simple, right?

Setting up the SP cloud

The configuration of the service provider cloud is done similarly to that of the identity provider. Below you can see the SP configuration block:

keystone_idp_id: my_idp
keystone_sp_id: my_sp

  cert_duration_years: 5
    - name: "{{ "{{ " }}keystone_idp_id{{ " }}" }}"
         - 'https://{{ "{{ " }}keystone_idp_host{{ " }}" }}:5000/v3/OS-FEDERATION/saml2/idp'
      metadata_uri: 'https://{{ "{{ " }}keystone_idp_host{{ " }}" }}:5000/v3/OS-FEDERATION/saml2/metadata'
      metadata_file: 'metadata-keystone-{{ "{{ " }}keystone_idp_id{{ " }}" }}.xml'
      metadata_reload: 1800
        - domain: Default
          project: fedproject
          group: fedgroup
          role: _member_
        - name: saml2
            - name: openstack_user
              id: openstack_user
            - name: openstack_roles
              id: openstack_roles
            - name: openstack_project
              id: openstack_project
            - name: openstack_user_domain
              id: openstack_user_domain
            - name: openstack_project_domain
              id: openstack_project_domain
            name: "{{ "{{ " }}keystone_idp_id{{ " }}" }}-mapping"
              - remote:
                  - type: openstack_user
                  - group:
                      name: fedgroup
                        name: Default
                      name: federated_user

keystone_token_provider: "keystone.token.providers.uuid.Provider"
keystone_token_driver: "keystone.token.persistence.backends.sql.Token"

Here the cert_duration_years configures the duration of a self-signed SSL certificate that will protect the endpoints used by the SAML2 protocol. The trusted_idp_list variable is the SP counterpart of the service_providers variable in the IdP configuration and defines the list of identity providers.

Like we did for SPs in the IdP side, here we have to provide a few settings for each IdP. These include the IdP’s unique identifier and its endpoints, plus a location where metadata associated with the IdP is to be stored. These can be set using custom variables.

The federated_identities defines sets of identities in the SP cloud that will be used with remote users. These can include a domain, project, group, role, or user. This is one part of the configuration that needs to be customized according to the needs of each SP cloud. In the above example, remote users will be put in the default domain, in a project called fedproject. The role will be the standard _member_ role, and users will be part of the fedgroup group. Any entities declared here will be automatically created by the keystone playbook.

The SP cloud needs to know how to map users of the IdP cloud as its own users, and this is done in the protocols variable. At this time, K2K only supports the saml2 protocol, so that is going to be the only entry.

The attributes defined by a protocol are the bits of information that the IdP shares with the SP when a user initiates an authentication request. Usually these are tied to the type of identity provider, so for a K2K setup, the attributes shown in the above example are the ones that will need to be declared. As you can see, these are the basic attributes of a user, which the SP can use to determine how to handle the user.

The protocol’s mapping section defines how the users of the IdP are to be mapped to local users and this is done through a list of rules. When the Keystone service running on the SP cloud receives a remote authentication, it will evaluate the remote portion of each rule until one matches the user. The matching criteria can be pretty simple or can also be fairly complex, involving one or more of the declared attributes. Once a matching rule has been found, the user is mapped as a local user according to the local part of the rule. In the example above, there is a single rule, which says that the remote user must have a declared openstack_user value (the username). The user will be mapped to the group fedgroup in the Default domain. I’m sure you noticed that the user given in the local part of the rule isn’t real. When remote users are mapped, ephemeral users are created to represent them.

The rule definition language allows for rules much more complex than the one shown above. For more information about federation mappings, you can consult the appropriate section of the Keystone documentation.

To configure your second cloud as a SP, add the above configuration to your /etc/openstack_deploy/user_variables.yml file, and, like in the IdP case, run the Keystone playbook:

# cd /opt/openstack-ansible/playbooks
# openstack-ansible os-keystone-install.yml

Finally, the SP configuration also needs UUID tokens to avoid issues with the default Fernet tokens.

At this point, the K2K federation between your two clouds should be fully configured and functional.

The K2K federation authentication flow

If you followed the instructions above, you have one of your clouds configured as an IdP, and the other configured as a SP. Not only that, the Keystone playbook in openstack-ansible also set things up so that the IdP cloud knows about the SP cloud, and the SP cloud knows about the IdP cloud.

So how does federation work? To begin, the user must authenticate against the IdP cloud. This is the standard authentication, so, for command line usage, this is usually achieved by importing an openrc file.

To initiate a federated request, the IdP cloud must contact the SP cloud and provide information about the user. For this, the IdP generates an assertion, which is an encrypted block of information about the user, and it sends it to the SP. The SP cloud will decrypt the assertion, verify it, and perform the mapping of the user. If the mapping is succesful, the SP cloud will return a token that the user can use to access the SP cloud.

The whole authentication process involves a few back and forths between the IdP and SP clouds. The openstack-ansible project provides a script that performs all the needed actions and provides the token for the IdP user to access the SP cloud as output.

To demonstrate how all this works, I’m going to copy this script to the utility container of my IdP, and then run it from there. Starting from a terminal on the IdP host, this is what you need to do:

# cd /opt/openstack-ansible
# scp scripts/ <utility-hostname>:~/
# ssh <utility-hostname>
# source openrc
# ./ --project fedproject --domain Default my_sp
Performing federated login...
- Obtained IdP token.
- Obtained SAML2 assertion from IdP.
- Submitted SAML2 assertion to SP.
- Obtained unscoped token from SP: 5236e3a6a185488a8fe7f84ff7edcdb4
- Domains available at sp:
- Projects  available at sp:
- Obtained scoped token from SP for project fedproject in domain Default: 1f6606af8cda4b27b787819f2eb3f2d4
- Full catalog available in file catalog.json
# Available endpoints:
# OpenStack client setup:
export OS_TOKEN=1f6606af8cda4b27b787819f2eb3f2d4
export OS_URL=<desired-service-endpoint>

The output of the shows a progress of all the actions taken during the authentication process and, once the authentication is completed, displays the information that you need to access the SP cloud.

From the output of the script, the important bits are the scoped token and the URLs for all the services. The token is going to be used with all the services, so it is best to put it in an environment variable that the openstack command line client automatically picks up, as suggested by the script:

# export OS_TOKEN=<scoped-token>

Then, for example, if you wanted to obtain a listing of all the images available to you in the SP cloud, you would use the image service endpoint as follows:

# openstack --os-endpoint= image list

To get a list of instances, the compute endpoint is used in a similar way:

# openstack --os-endpoint= server list

You are probably thinking that it is inconvenient to have to provide the service endpoint for each command, given that when accessing the local cloud the openstack command line client can figure that out on its own from the service catalog. I will discuss this and other problems with the current state of K2K federation in the next section.

Current limitations of K2K

Now that you’ve seen, and maybe even experienced, K2K federation, I’m sure you are scratching your head and wondering why things aren’t more streamlined. In this section, I have compiled a short list of problems you may run into when using K2K federation with the Kilo release of OpenStack.

Horizon support

For starters, you may be wondering if it is possible to log in from the Horizon dashboard and have a more friendly way to interact with a remote cloud. The unfortunate answer is no, because the implementation of the SAML2 federation protocol in Keystone is incomplete. The SP side has support for the “websso” flow, which enables Horizon to connect to an external IdP, but the Keystone IdP implementation does not currently support websso, restricting Horizon to only connect to third party IdPs at this time. An example IdP that works well with Horizon is the Active Directory Federation Service from Microsoft (ADFS).

Command line client support

In the previous section, you saw that to use the openstack command line client with federation you have to provide a token and the endpoint of the service you want to connect to. When working with a local OpenStack cloud, the clients can connect to the Keystone service to request a token and the service catalog, and can then obtain the required endpoint from this catalog. This all happens transparently during the authentication process, the command line clients know how to do all this for you.

At this time, the authentication flow for K2K is not fully integrated with the OpenStack clients, so a fully automated authentication similar to that of a local cloud is not possible. Work on a K2K federation authentication extension for Keystone is currently in progress, so this limitation is likely going to be a non-issue in the Liberty release. My hope is that with some additional variables added to the user’s openrc file, the command line clients can perform the complete federated authentication, similar to the wrapper scripts included with openstack-ansible, and with automated endpoint lookup. We’ll see if this becomes a reality.

Fernet tokens and federation

While working on the federation support for openstack-ansible, we noticed that there were problems with federated tokens when the Keystone service in the SP cloud is configured to use Fernet tokens. There is a fix made towards the Liberty release, but that fix has not been backported to Kilo yet. Hopefully by the time you read this, the fix will be publicly available. But if you see that the wrapper script fails to obtain a token, you have to switch the Keystone service in both clouds to UUID tokens, which as you saw above, you can do by adding these variables to your user_variables.yml file:

keystone_token_provider: "keystone.token.providers.uuid.Provider"
keystone_token_driver: "keystone.token.persistence.backends.sql.Token"

Final words

I hope this article was helpful in giving you an introduction to the K2K federation features in the Kilo release. And if you weren’t familiar with the openstack-ansible project, I hope I said enough good things about it that you will decide to check it out in detail, even if you don’t plan to use federation.

My intention is to write a follow up federation article when the Liberty release ships. I hope by that time some of the problems I enumerated in this article will have a solution.

Thank you!


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Miguel Grinberg

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