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Guacamole supports Duo as a second authentication factor, layered on top of any other authentication extension, including those available from the main project website. The Duo authentication extension allows users to be additionally verified against the Duo service before the authentication process is allowed to succeed.
Important
This chapter involves modifying the contents of GUACAMOLE_HOME -
the Guacamole configuration directory. If you are unsure where
GUACAMOLE_HOME is located on your system, please consult Chapter 5, Configuring Guacamole before proceeding.
Guacamole provides support for Duo as a second authentication factor. To make use of the Duo authentication extension, some other authentication mechanism will need be configured, as well. When a user attempts to log into Guacamole, other installed authentication methods will be queried first:
Only after authentication has succeeded with one of those methods will Guacamole reach out to Duo to obtain additional verification of user identity:
If both the initial authentication attempt and verification through Duo succeed, the user will be allowed in. If either mechanism fails, access to Guacamole is denied.
The Duo 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.incubator.apache.org/releases/.
The Duo authentication extension is packaged as a .tar.gz file
containing only the extension itself,
guacamole-auth-duo-0.9.13-incubating.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. To install
the Duo authentication extension, you must:
Create the
GUACAMOLE_HOME/extensionsdirectory, if it does not already exist.Copy
guacamole-auth-duo-0.9.13-incubating.jarwithinGUACAMOLE_HOME/extensions.Configure Guacamole to use Duo authentication, as described below.
Important
You will need to restart Guacamole by restarting your servlet container in order to complete the installation. Doing this will disconnect all active users, so be sure that it is safe to do so prior to attempting installation. If you do not configure the Duo authentication properly, Guacamole will not start up again until the configuration is fixed.
Duo does not provide a specific integration option for Guacamole, but Guacamole's Duo extension uses Duo's generic authentication API which they refer to as the "Web SDK". To use Guacamole with Duo, you will need to add it as a new "Web SDK" application from within the "Applications" tab of the admin panel of your Duo account:
Within the settings of the newly-added application, rename the application to something more representative than "Web SDK". This application name is what will be presented to your users when they are prompted by Duo for additional authentication:
Once you've finished adding Guacamole as an "Web SDK" application, the
configuration information required to configure Guacamole is listed within the
application's "Details" section. You will need to copy the integration key, secret
key, and API hostname - they will later be specified within
guacamole.properties:
The application-specific configuration information retrieved from Duo must be
added to guacamole.properties to describe how Guacamole should
connect to the Duo service:
- duo-api-hostname
The hostname of the Duo API endpoint to be used to verify user identities. This will usually be in the form "
api-", where "XXXXXXXX.duosecurity.comXXXXXXXX" is some arbitrary alphanumeric value assigned by Duo. This value will have been generated by Duo when you added Guacamole as an "Web SDK" application, and can be found within the application details in the "API hostname" field. This value is required.- duo-integration-key
The integration key provided for Guacamole by Duo. This value will have been generated by Duo when you added Guacamole as an "Web SDK" application, and can be found within the application details in the "Integration key" field. This value is required and must be EXACTLY 20 characters.
- duo-secret-key
The secret key provided for Guacamole by Duo. This value will have been generated by Duo when you added Guacamole as an "Web SDK" application, and can be found within the application details in the "Secret key" field. This value is required and must be EXACTLY 20 characters.
In addition to the above, you must also manually generate an "application key". The application key is required by Duo's authentication API, but is not provided by Duo. It is an arbitrary value meant to be unique to each deployment of an application using their API.
- duo-application-key
An arbitrary, random key which you manually generated for Guacamole. This value is required and must be AT LEAST 40 characters.
The application key can be generated with any method as long as it is sufficiently random. There exist utilities which will do this for you, like pwgen:
$pwgen 40 1em1io4zievohneeseiwah0zie2raQuoo2ci5oBoo$
Alternatively, one quick and fairly portable way to do this is to use the
dd utility to copy random bytes from the secure random device
/dev/random, sending the data through a cryptographic hash
tool with a sufficiently-long result, like sha256sum:
$dd if=/dev/random count=1 | sha256sum5d16d6bb86da73e7d1abd3286b21dcf3b3e707532e64ceebc7a008350d0d485d -$
Guacamole will only reread guacamole.properties and load
newly-installed extensions during startup, so your servlet container will need to be
restarted before Duo authentication will take effect. Restart your servlet container
and give the new authentication a try.
Important
You only need to restart your servlet container. You do not need to restart guacd.
guacd is completely independent of the web application
and does not deal with guacamole.properties or the
authentication system in any way. Since you are already restarting the
servlet container, restarting guacd as well technically
won't hurt anything, but doing so is completely pointless.
If Guacamole does not come back online after restarting your servlet container, check the logs. Problems in the configuration of the Duo extension may prevent Guacamole from starting up, and any such errors will be recorded in the logs of your servlet container.