SAML Authentication

SAML is a widely implemented and used Single Sign On (SSO) provider that allows applications and services to authenticate in a standard way, and brokers those authentication requests to one or more back-end authentication providers. The SAML authentication extension allows Guacamole to redirect to a SAML Identity Provider (IdP) for authentication and user services. This module does not provide any capability for storing or retrieving connections, and must be layered with other authentication extensions that provide connection management.

Downloading the SAML authentication extension

Guacamole’s SSO extensions are 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 SSO extensions are packaged together in a .tar.gz file containing one extension for each supported SSO method:

SSO Method	Extension
CAS	cas/guacamole-auth-sso-cas-1.5.4.jar
OpenID Connect	openid/guacamole-auth-sso-openid-1.5.4.jar
SAML	saml/guacamole-auth-sso-saml-1.5.4.jar

The extension for the desired SSO method, in this case guacamole-auth-sso-saml-1.5.4.jar from within the saml/ subdirectory, must ultimately be placed in GUACAMOLE_HOME/extensions.

Installing SAML authentication

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 Configuring Guacamole before proceeding.

To install the SAML authentication extension, you must:

1. Create the GUACAMOLE_HOME/extensions directory, if it does not already exist.

2. Copy guacamole-auth-sso-saml-1.5.4.jar within GUACAMOLE_HOME/extensions.

3. Configure Guacamole to use SAML authentication, as described below.

Configuring Guacamole for SAML Authentication

The SAML authentication extension provides several configuration properties to set it up to talk to the IdP. The SAML IdP also must be configured with Guacamole as a Service Provider (SP). Configuration of the SAML IdP is beyond the scope of this document, and will vary widely based on the IdP in use.

saml-idp-metadata-url

The URI of the XML metadata file that from the SAML Identity Provider that contains all of the information the SAML extension needs in order to know how to authenticate with the IdP. This URI can either be a remote server (e.g. https://) or a local file on the filesystem (e.g. file://). Often the metadata file contains most of the required properties for SAML authentication and the other parameters are not required.

saml-idp-url

The base URL of the SAML IdP. This is the URL that the SAML authentication extension will use to redirect when requesting SAML authentication. If the saml-idp-metadata-url property is provided, this parameter will be ignored. If the metadata file is not provided this property is required.

saml-entity-id

The entity ID of the Guacamole SAML client, which is generally the URL of the Guacamole server, but is not required to be so. This property is required if either the saml-idp-metadata-url property is not specified, or if the provided metadata file does not contain the SAML SP Entity ID for Guacamole Client.

saml-callback-url

The URL that the IdP will use once authentication has succeeded to return to the Guacamole web application and provide the authentication details to the SAML extension. The SAML extension currently only supports callback as a POST operation to this callback URL. This property is required.

saml-strict

Require strict security checks during SAML logins. This will insure that valid certificates are present for all interactions with SAML servers and fail SAML authentication if security restrictions are violated. This property is optional, and will default to true, requiring strict security checks. This property should only be set to false in non-production environments during testing of SAML authentication.

saml-debug

Enable additional logging within the supporting SAML library that can assist in tracking down issues during SAML logins. This property is optional, and will default to false (no debugging).

saml-compress-request

Enable compression of the HTTP requests sent to the SAML IdP. This property is optional and will default to true (compression enabled).

saml-compress-response

Request that the SAML response returned by the IdP be compressed. This property is optional and will default to true (compression will be requested).

saml-group-attribute

The name of the attribute provided by the SAML IdP that contains group membership of the user. These groups will be parsed and used to map group membership of the user logging in, which can be used for permissions management within Guacamole Client, particularly when layered with other authentication modules. This property is optional, and defaults to “groups”.

Controlling login behavior

Guacamole loads authentication extensions in order of priority, and evaluates authentication attempts in this same order. This has implications for how the Guacamole login process behaves when an SSO extension is present:

If the SSO extension has priority:

Users that are not yet authenticated will be immediately redirected to the configured identity provider. They will not see a Guacamole login screen.

If a non-SSO extension has priority:

Users that are not yet authenticated will be presented with a Guacamole login screen. Additionally, links to the configured identity provider(s) will be available for users that wish to log in using SSO.

The default priority of extensions is dictated by their filenames, with extensions that sort earlier alphabetically having higher priority than others. This can be overridden by setting the extension-priority property within guacamole.properties.

Automatically redirecting all unauthenticated users

To ensure users are redirected to the SAML identity provider immediately (without a Guacamole login screen), ensure the SAML extension has priority over all others:

extension-priority: saml

Presenting unauthenticated users with a login screen

To ensure users are given a normal Guacamole login screen and have the option to log in with traditional credentials or with SAML, ensure the SAML extension does not have priority:

extension-priority: *, saml

Completing the installation

Guacamole will only reread guacamole.properties and load newly-installed extensions during startup, so your servlet container will need to be restarted before SAML 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.