The main goal of this charm is to generate the necessary configuration for use in the Keystone charm related to Service Provider config generation, trust establishment between a remote idP and SP via certificates and signaling Keystone service restart. Keystone has a concept of a federated backend which serves multiple purposes including being a backend part of a Service Provider in an authentication scenario where SAML is used. Unless ECP is used on a keystone client side, SAML-related exchange is performed in an Apache authentication module (Mellon in case of this charm) and SAML assertions are converted to WSGI environment variables passed down to a particular mod_wsgi interpreter running Keystone code. Keystone has an authentication plug-in called "mapped" which does the rest of the work of resolving symbolic attributes and using them in mappings defined by an operator or validating the existence of referenced IDs.
This subordinate charm provides a way to integrate a SAML-based identity
provider with Keystone using Mellon Apache web server authentication
module (mod_auth_mellon) and lasso as its dependency. Mellon acts as a
Service Provider in this case and provides SAML token attributes as WSGI
environment variables to Keystone which does not itself participate in
SAML exchanges - it merely interprets results of such exchanges
and maps assertion-derived attributes to entities (such as groups,
roles, projects and domains) in a local Keystone SQL database.
In general, any identity provider that conforms to SAML 2.0 will be
possible to integrate using this charm.
The following documentation is useful to better understand the charm
Use this charm with the Keystone charm, running with preferred-api-version=3:
juju deploy keystone
juju config keystone preferred-api-version=3 # other settings
juju deploy openstack-dashboard # settings
juju deploy keystone-saml-mellon
juju add-relation keystone keystone-saml-mellon
juju add-relation keystone openstack-dashboard
In a bundle:
user-facing-name: "myidp via saml2'
- [ keystone, keystone-saml-mellon ]
- [ openstack-dashboard, keystone-saml-mellon ]
- [ "openstack-dashboard:websso-trusted-dashboard", "keystone:websso-trusted-dashboard" ]
In order to use this charm, there are several prerequisites that need to be
taken into account which require certain infrastructure to be set up out of
On the Keystone charm side, this means that ssl_ca, ssl_cert, ssl_key,
use-https and os-public-hostname must be set.
Several key pairs can be used in a generic SAML exchange along with
certificates containing public keys. Besides the pairs used for message-level
signing and encryption there are also TLS certificates used for transport
layer encryption when a browser connects to a protected URL on the SP side or
when it gets redirected to an idP endpoint for authentication. In summary:
For a successful authentication to happen the following needs to hold:
Note that this does not mean that any actual checks are performed for
certificates related to SAML - only key material is used and there does
NOT have to be any PKI actually in-place, not even expiration times are
checked as per Mellon documentation. In that sense trust is very explicitly
defined by out of band mutual synchronization of SP and idP metadata files.
See SAML V2.0 Metadata Interoperability Profile (2.6.1) key processing
section for a normative reference.
However, this does not mean that no PKI will be in place - TLS certificates
used for HTTPS connectivity have to be verifiable by the entities that use
them. With Redirect or POST binding this is mainly about user agent being
able to validate SP or idP certificates - there is no direct communication
between the two outside the metadata synchronization step which is performed
by an operator out of band.
Additionally, for successful certificate verification clocks of all parties
need to be properly synchronized which is why it is important for NTP agents
to be able to reach proper NTP servers on SP and idP.
There are several post-deployment steps that have to be performed in order to
start using federated identity functionality in Keystone. They depend on the
chosen config values and also on an IDP configuration as it may put different
NameID values and attributes into SAML tokens. Token attributes are parsed by
mod_auth_mellon and are placed into WSGI environment which are used by
Keystone and they have the following format: "MELLON_"
(one attribute can have multiple values in SAML). Both NameID and attribute
values can be used in mappings to map SAML token content to existing and, in
case of projects, potentially non-existing entities in Keystone database.
In order to take the above into account several objects need to be created:
cat > rules.json <<EOF
openstack domain create federated_domain
openstack project create federated_project --domain federated_domain
openstack group create federated_users --domain federated_domain
# created group id: 0427a780b34441488f064526a9890edd
openstack role add --group 0427a780b34441488f064526a9890edd --domain federated_domain Member
openstack identity provider create --remote-id https://adfs.intranet.test/adfs/services/trust myidp
openstack mapping create --rules rules.json myidp_mapping
openstack federation protocol create mapped --mapping myidp_mapping --identity-provider myidp
# list related projects
openstack federation project list
Please report bugs on Launchpad.
For general questions please refer to the OpenStack Charm Guide.