To secure access to your Tomcat webapp, you can implement your simple security constraint (e.g. in /var/lib/tomcat7/webapps/*/WEB-INF/web.xml) as below (just add it before </web-app> ending):
<!-- This security constraint protects your webapp interface. -->
<login-config>
<!-- Define the Login Configuration -->
<auth-method>BASIC</auth-method>
<realm-name>Webapp</realm-name>
</login-config>
<security-constraint>
<web-resource-collection>
<web-resource-name>Admin</web-resource-name>
<url-pattern>/*</url-pattern>
<http-method>GET</http-method>
<http-method>POST</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>*</role-name>
</auth-constraint>
<!-- Specifying a Secure Connection -->
<user-data-constraint>
<!-- transport-guarantee can be CONFIDENTIAL (forced SSL), INTEGRAL, or NONE -->
<transport-guarantee>NONE</transport-guarantee>
</user-data-constraint>
</security-constraint>
<!-- Authorization, see: tomcat-users.xml -->
<security-role>
<role-name>*</role-name>
</security-role>
The login-config element contains the auth-method element, which specifies the authentication method that we use, which is BASIC. The security-constraint element contains 3 elements: web-resource-collection, auth-constraint, and user-data-constraint. The web-resource-collection specifies the parts of our application that require authentication. The /* indicates that the whole application requires authentication. The auth-constraint specifies the role that a user needs to have in order to access the protected resources. The user-data-constraint's transport-guarantee can be NONE, CONFIDENTIAL or INTEGRAL. We set it to NONE, which means that redirecting to SSL is not required when you try to hit the protected resource.
Also make sure that you've line:
<Realm className="org.apache.catalina.realm.MemoryRealm" />
inside your conf/server.xml (Engine section).
If you have not changed any configuration files, please examine the file conf/tomcat-users.xml in your installation (locate tomcat-users.xml). That file must contain the credentials to let you use Tomcat webapp.
For example, to add the manager-gui role to a user named tomcat with a password of s3cret, add the following to the config file listed above:
<role rolename="manager-gui"/>
<user username="tomcat" password="s3cret" roles="manager-gui"/>
Then you can access your webapps manager from /manager/html (e.g. reloading after config changes).
Read more: Manager App HOW-TO.
Then restart your Tomcat and when accessing your webapp, it should ask you for the right credentials.
See also: