Wednesday, October 26, 2016

Switching authentication mechanisms in the Apache CXF Fediz STS

Apache CXF Fediz ships with an Identity Provider (IdP) that can authenticate users via either the WS-Federation or SAML SSO protocols. The IdP delegates user authentication to a Security Token Service (STS) web application using the WS-Trust protocol. The STS implementation in Fediz ships with some sample user data for use in the tests. For a real-world scenario, deployers will have to swap the sample data out for an identity backend (such as Active Directory or LDAP). This post will explain how this can be done, with a particular focus on some recent changes to the STS web application in Fediz to make the process easier.

1) The default STS that ships with Fediz

First let's explain a bit about how the STS is configured by default in Fediz to cater for the testcases.

a) Endpoints and user authentication

The STS must define two distinct set of endpoints to work with the IdP. Firstly, the STS must be able to authenticate the user credentials that are presented to the IdP. Typically this is a Username + Password combination. However, X.509 client certificates and Kerberos tokens are also supported. Note that by default, the STS authenticates usernames and passwords via a simple file local to the STS.

After successful user authentication, a SAML token is returned to the IdP. The IdP then gets another SAML token "on behalf of" the authenticated user for a given realm, authenticating using its own credentials. So we need a second endpoint in the STS to issue this token. By default, the STS requires that the IdP authenticate using TLS client authentication. The security policies are defined in the WSDLs available here.

b) Realms

The Fediz IdP and STS support the concept of authenticating users in different realms. By default, the IdP is configured to authenticate users in "Realm A". This corresponds to a specific endpoint address in the STS. The STS also defines user authentication endpoints in "Realm B" for use in test scenarios involving identity federation between two IdPs.

In addition, the STS defines some configuration to map user identities between realms. In other words, how a principal in one realm should map to another realm, and how the claims in one realm map to those in another realm.

2) Changing the STS in Fediz 1.3.2 to use LDAP

From the forthcoming 1.3.2 release onwards, the Fediz STS web application is a bit easier to customize for your specific deployment needs. Let's see how easy it is to switch the STS to use LDAP.

a) Deploy the vanilla IdP and STS to Apache Tomcat

To start with, we will deploy the STS and IdP containing the sample data to Apache Tomcat.
  • Create a new directory: ${catalina.home}/lib/fediz
  • Edit ${catalina.home}/conf/ and append ',${catalina.home}/lib/fediz/*.jar' to the 'common.loader' property.
  • Copy ${fediz.home}/plugins/tomcat/lib/* to ${catalina.home}/lib/fediz
  • Copy ${fediz.home}/idp/war/* to ${catalina.home}/webapps
  • Download and copy the hsqldb jar (e.g. hsqldb-2.3.4.jar) to ${catalina.home}/lib 
  • Copy idp-ssl-key.jks and idp-ssl-trust.jks from ${fediz.home}/examples/sampleKeys to ${catalina.home}
  • Edit the TLS Connector in ${catalina.home}/conf/server.xml', e.g.: <Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol" maxThreads="150" SSLEnabled="true" scheme="https" secure="true" clientAuth="want" sslProtocol="TLS" keystoreFile="idp-ssl-key.jks" keystorePass="tompass" keyPass="tompass" truststoreFile="idp-ssl-trust.jks" truststorePass="ispass" />
Now start Tomcat and then enter the following in a web browser (authenticating with "alice/ecila" in "realm A" - you should be directed to the URL for the default service application (404, as we have not configured it):


b) Change the STS authentication mechanism to Active Directory

To simulate an Active Directory instance for demonstration purposes, we will modify some LDAP system tests in the Fediz source that use Apache Directory. Check out the Fediz source and build it via "mvn install -DskipTests". Now go into "systests/ldap" and edit the LDAPTest. "@Ignore" the existing test + uncomment the test which just "sleeps". Also change the "@CreateTransport" annotation to start the LDAP port on "12345" instead of a random port.

Next we'll configure the Fediz STS to use this LDAP instance for authentication. Edit 'webapps/fediz-idp-sts/WEB-INF/cxf-transport.xml'. Change "endpoints/file.xml" to "endpoints/ldap.xml". Next edit 'webapps/fediz-idp-sts/WEB-INF/endpoints/ldap.xml" and just change the port from "389" to "12345".

Now we need to configure a JAAS configuration file, which the STS uses to validate the received Username + Password to LDAP. Copy this file to the "conf" directory of Tomcat, substituting "12345" for "portno". Now restart Tomcat, this time specifying the location of the JAAS configuration file, e.g.:
  • export JAVA_OPTS="-Xmx2048M"
This is all the changes that are required to swap over to use an LDAP instance for authentication.