TCAT-AS-000860 - Clusters must operate on a trusted network.
Operating a Tomcat cluster on an untrusted network creates potential for unauthorized persons to view or manipulate cluster session traffic. When operating a Tomcat cluster, care must be taken to isolate the cluster traffic from untrusted sources. Options include using a private VLAN, VPN, or IPSEC tunnel or by encrypting cluster traffic by using the EncryptInterceptor. The EncryptInterceptor adds encryption to the channel messages carrying session data between Tomcat cluster nodes. Place the <Cluster> element inside either the <Engine> container or the <Host> container. Placing it in the engine means supporting clustering in all virtual hosts of Tomcat and sharing the messaging component. When the user places the <Cluster> inside the <Engine> element, the cluster will append the host name of each session manager to the manager's name so that two contexts with the same name (but sitting inside two different hosts) will be distinguishable.
Update the System Security Plan (SSP) and document the network interface, their related IP addresses, and which interfaces transport Tomcat cluster traffic. Also document which interface is multi-cast enabled if using the McastService membership class versus Static. To obtain the information needed for the SSP: sudo grep -i -A3 '<Membership className' $CATALINA_BASE/conf.server.xml Document the address='<ipAddress>' value. Review the OS routing tables. Identify and document which interface is configured to route the Tomcat class D IP multicast traffic. sudo netstat -r END of Documentation instructions. From the Tomcat server as a privileged user, edit the $CATALINA_BASE/conf/server.xml file. sudo nano $CATALINA_BASE/conf/server.xml Locate the <Interceptor/> element nested within the <Channel/> element. Add the <Interceptor className='org.apache.catalina.tribes.group. interceptors.EncryptInterceptor'/> to the server.xml and save the file. Restart the Tomcat server: sudo systemctl restart tomcat NOTE: The EncryptInterceptor adds encryption to the channel messages carrying session data between nodes. This feature was added in Tomcat 9.0.13. If using the TcpFailureDetector interceptor, the EncryptInterceptor must be inserted into the interceptor chain BEFORE the TcpFailureDetector. When validating cluster members, TcpFailureDetector writes channel data directly to the other members without using the remainder of the interceptor chain, but on the receiving side, the message still goes through the chain (in reverse). Because of this asymmetry, the EncryptInterceptor must execute before the TcpFailureDetector on the sender and after it on the receiver; otherwise, message corruption will occur.