Table of Contents
CAS is an open-source Single Sign On (SSO) provider that allows multiple applications and services to authenticate against it and brokers those authentication requests to a back-end authentication provider. This module allows Guacamole to redirect to CAS for authentication and user services. This module must be layered on top of other authentication extensions that provide connection information, as it only provides user authentication.
The CAS authentication extension is available separately from the main
guacamole.war
. The link for this and all other
officially-supported and compatible extensions for a particular version of Guacamole are
provided on the release notes for that version. You can find the release notes for
current versions of Guacamole here: http://guacamole.apache.org/releases/.
The CAS authentication extension is packaged as a .tar.gz
file containing only the extension itself,
guacamole-auth-cas-1.3.0.jar
, which must
ultimately be placed in GUACAMOLE_HOME/extensions
.
Guacamole extensions are self-contained .jar
files which are
located within the GUACAMOLE_HOME/extensions
directory.
If you are unsure where GUACAMOLE_HOME
is located on
your system, please consult Chapter 5, Configuring Guacamole before
proceeding.
To install the CAS authentication extension, you must:
Create the
GUACAMOLE_HOME/extensions
directory, if it does not already exist.Copy
guacamole-auth-cas-1.3.0.jar
withinGUACAMOLE_HOME/extensions
.Configure Guacamole to use CAS authentication, as described below.
Guacamole's CAS support requires specifying two properties that describe the CAS authentication server and the Guacamole deployment. These properties are absolutely required in all cases, as they dictate how Guacamole should connect to the CAS and how CAS should redirect users back to Guacamole once their identity has been confirmed:
- cas-authorization-endpoint
The URL of the CAS authentication server. This should be the full path to the base of the CAS installation.
- cas-redirect-uri
The URI to redirect back to upon successful authentication. Normally this will be the full URL of your Guacamole installation.
Additional optional properties are available to control how CAS tokens are processed, including whether CAS ClearPass should be used and how user group memberships should be derived:
- cas-clearpass-key
If using CAS ClearPass to pass the SSO password to Guacamole, this parameter specifies the private key file to use to decrypt the password. See the section on ClearPass below.
- cas-group-attribute
The CAS attribute that determines group membership, typically "memberOf". This parameter is only required if using CAS to define user group memberships. If omitted, groups aren't retrieved from CAS, and all other group-related properties for CAS are ignored.
- cas-group-format
The format that CAS will use for its group names. Possible values are
plain
, for groups that are simple text names, orldap
, for groups that are represented as LDAP DNs. If set toldap
, group names are always determined from the last (leftmost) attribute of the DN. If omitted,plain
is used by default.This property has no effect if cas-group-attribute is not set.
- cas-group-ldap-base-dn
The base DN to require for LDAP-formatted CAS groups. If specified, only CAS groups beneath this DN will be included, and all other CAS groups will be ignored.
This property has no effect if cas-group-format is not
ldap
.- cas-group-ldap-attribute
The LDAP attribute to require for LDAP-formatted CAS groups. If specified, only CAS groups that use this attribute for the name of the group will be included. Note that LDAP group names are always determined from the last (leftmost) attribute of the DN. Specifying this property will only have the effect of ignoring any groups that do not use the specified attribute to represent the group name.
This property has no effect if cas-group-format is not
ldap
.
Guacamole will only reread guacamole.properties
and load
newly-installed extensions during startup, so your servlet container will need to be
restarted before CAS authentication can be used. Doing this will
disconnect all active users, so be sure that it is safe to do so prior to
attempting installation. When ready, restart your servlet container
and give the new authentication a try.
CAS has a function called ClearPass that can be used to cache the password used for SSO authentication and make that available to services at a later time. Configuring the CAS server for ClearPass is beyond the scope of this article - more information can be found on the Apereo CAS wiki at the following URL: https://apereo.github.io/cas.
Once you have CAS configured for credential caching, you need to configure the service with a keypair for passing the credential securely. The public key gets installed on the CAS server, while the private key gets configured with the cas-clearpass-key property. The private key file needs to be in RSA PKCS8 format.