How to Implement SSO on existing tomcat web application

I have managed this with the Tomcat's SSO Valve:

1. Put SSO Valve within Host (localhost) element of server.xml file:

   <Host appBase="webapps" autoDeploy="true" name="localhost" unpackWARs="true"> <Valve className="org.apache.catalina.authenticator.SingleSignOn" /> </Host>

2. Add users and roles (eg. in tomcat_users.xml):

   <user username="user1" password="user1" roles="employee"/>

3. In web-app element of your app's web.xml file, add security constraints:

   <security-constraint> <web-resource-collection> <web-resource-name>App name</web-resource-name> <url-pattern>/*</url-pattern> </web-resource-collection> <auth-constraint> <role-name>employee</role-name> </auth-constraint> </security-constraint> <login-config> <auth-method>FORM</auth-method> <realm-name>file</realm-name> <form-login-config> <form-login-page>/login.jsp</form-login-page> <form-error-page>/error.jsp</form-error-page> </form-login-config> </login-config> <security-role> <role-name>employee</role-name> </security-role>

4. That's it. Now, log in to the one of your apps, and you should be logged in to other apps.

Of course, you should not use a plain text password in the production, this is just a quick example. You shoud consider Digest authentication, as well as configuring SSL on Tomcat.

I hope this will help someone!

P.S. if you store users in the SQL database, please check my comment below this answer.

You can implement SSO in many different ways:

1. Oauth 2 - http://oauth.net/2/
2. SAML 2 - https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=security

SAML 2.0 has many implementations for Identity/Service provider roles.

For an IDP implementations list I can point you to this stackoverflow post: https://stackoverflow.com/a/761774/126414

If you are planning to implement a service provider there is a nice spring extension: http://static.springsource.org/spring-security/site/extensions/saml/index.html

Update: Its 2018 and the below info is out of date. If you’re starting a new application then use a federated identity protocol like Open ID Connect and you’ll get SSO for free.

There are a few approaches you could take:

1. You could use Tomcat for authentication and use Tomcat's single sign on capabilities. If you're currently using Spring to authenticate the user you may need to change some things. Also, depending on how you're doing authentication, Tomcat's authentication may not be configurable enough.
2. You could setup a third, CAS, servlet (or something similar), which both web applications authenticate against.
3. You could set this up yourself using Spring and pre-authenticated filters. You would basically have to write your own pre-authenticated filter which checked some location that both servlets had access to (database?, shared context?) for existing credentials before falling back to old authentication methods. You'll want to make sure to clear this authentication in a filter somewhere so the next request doesn't get to automatically inherit the previous requests credentials.