Configuring Apache HTTPS Reverse-Proxy

Exposing OpenKM directly from Tomcat can be dangerous if you need the application to be accessed from the Internet (for example https://issues.jboss.org/browse/JBAS-3861). As a result, you can be infected by PerlBot. Also, port 8080 may be blocked by a firewall. For these reasons, it is a good practice to expose your OpenKM installation through the standard web port 80. In the following steps we explain how to configure Apache to handle these requests and forward them to the Tomcat application server using the AJP13 protocol.

From the Apache documentation: The AJP13 protocol is packet-oriented. A binary format was presumably chosen over the more readable plain text for performance reasons. The web server communicates with the servlet container over TCP connections. To cut down on the expensive process of socket creation, the web server will attempt to maintain persistent TCP connections to the servlet container, and to reuse a connection for multiple request/response cycles.

Internal IP vs external IP

Your OpenKM can be accessed from two different zones: the Internet and the LAN. This means that to access this server you need to use two IP addresses: an external IP (Internet) and an internal IP (LAN).

The internal IP address (also known as the "local IP address") is the address that is assigned by your local network router and often begins with 192.168.x.x. These IP addresses can only be seen by other computers in your local network (LAN) and not by any computer connected in an external network such as the Internet.

To reach the Internet or a computer in another network, your computer is often assigned an external IP address, which can then be used to refer to the computer in your local network.

In the above picture, there are three computers in the local network that have each been assigned their own internal IP address by the router. The ISP is connected to the router and gives the router an external IP address that allows it to communicate with the Internet. On the Internet everyone sees your external IP address, but any information coming from the router is "converted" from the external IP address to the internal IP address.

So if you want your OpenKM installation to be accessible from both the LAN and the Internet, the trick here is to configure the client computers to resolve your internal IP (192.168.0.50) if they are inside the LAN or the external IP if they are on the Internet. To resolve the Internet IP (67.166.214.148), your computer uses the public DNS. So, you need to configure a DNS server inside the LAN or modify every client host file to resolve to the internal IP.

Debian and Ubuntu

The first thing is to install the required Apache software. On Debian/Ubuntu you can install Apache with a single command:

Edit the file named /etc/apache2/apache2.conf and configure a ServerName to prevent warnings in the Apache startup process:

ServerRoot "/etc/apache2"
ServerName "your-domain.com"

Enable the proxy module:

 Create the certificates

Ensure port 443 is listed in /etc/apache2/ports.conf:

Create the configuration file /etc/apache2/sites-available/openkm.conf with this content:  

<VirtualHost *:443>
  ServerName openkm.your-domain.com
  RedirectMatch ^/$ /openkm

  # WebSocket support - needs proxy-wstunnel
  ProxyPass /openkm/frontend/webSocket wss://127.0.0.1:8080/openkm/frontend/webSocket
  ProxyPassReverse /openkm/frontend/webSocket wss://127.0.0.1:8080/openkm/frontend/webSocket

  ProxyPass /openkm ajp://127.0.0.1:8009/openkm
  ProxyPassReverse /openkm https://openkm.your-domain.com/openkm

  ErrorLog /var/log/apache2/openkm.your-domain.com-error.log
  CustomLog /var/log/apache2/openkm.your-domain.com-access.log combined
 
  SSLEngine on
  SSLCertificateFile /etc/apache2/ssl/apache.pem
</VirtualHost>

The VirtualHost ServerName must be different from the ServerName in the main Apache configuration. Enable this site configuration:

Redirect all HTTP connections to HTTPS

Edit the configuration file /etc/apache2/sites-available/openkm.conf and add the following content 

<VirtualHost *:80>
  ServerName openkm.your-domain.com
  Redirect permanent / https://openkm.your-domain.com/
</VirtualHost>

Check the configuration

Restart Apache:

Check access to your OpenKM installation at https://openkm.your-domain.com/.  

Using Let's Encrypt

Let's Encrypt is a free certificate authority that provides X.509 certificates for Transport Layer Security (TLS) encryption at no charge. To be able to request and install the certificates you need the certbot utility. If you're using Apache, you also need the certbot-apache package:

Once installed, execute the utility with these parameters:

This certificate will be valid for 90 days, so you need to renew it before it expires. It's a good practice to create a cron task to update it automatically:

Also keep in mind that both ports 80 and 443 should be accessible from the Internet to validate the domain and generate the certificate.

Red Hat and CentOS

Use the yum package manager to install Apache:

Enable it at boot:

Create the certificate

Generate private keys (for more information, visit Apache HTTP Secure Server Configuration).

During the process, two files will be generated at:

Now create the file /etc/httpd/conf.d/openkm.conf with this content:

<VirtualHost *:443>
  ServerName openkm.your-domain.com
  ProxyPass / ajp://localhost:8009/openkm/
  ProxyPassReverse / http://your-domain.com/openkm/
  ErrorLog /var/log/your-domain.com-error.log
  CustomLog /var/log/your-domain.com-access.log combined
 
  SSLEngine on
  SSLCertificateFile /etc/pki/tls/certs/your-domain.com.cert
  SSLCertificateKeyFile /etc/pki/tls/private/your-domain.com.key
</VirtualHost>

Finally, modify the SSLCertificateFile and SSLCertificateKeyFile values in the file /etc/httpd/conf.d/ssl.conf:

SSLCertificateFile /etc/pki/tls/certs/your-domain.com.cert
SSLCertificateKeyFile /etc/pki/tls/private/your-domain.com.key

Check the configuration

Restart Apache:

Check access to your OpenKM installation at https://openkm.your-domain.com/.  

Error Permission denied: proxy: AJP: attempt to connect

If the log shows an error like Permission denied: proxy: AJP: attempt to connect, solve it by executing the following command:

If it works, then make the configuration permanent to persist across reboots:

Windows

Please read Configuring Apache HTTP Reverse-Proxy 

Troubleshooting

If you see an error like:

You need to enable these Apache modules:  

If you see errors like these:

It is possible that Tomcat is not accepting AJP connections. Please uncomment these lines in $TOMCAT_HOME/conf/server.xml

<!-- Define an AJP 1.3 Connector on port 8009 -->
<Connector protocol="AJP/1.3"
           address="127.0.0.1"
           port="8009"
           redirectPort="8443"
           secretRequired="false" />

The secretRequired parameter is important, and if it's not present you need to add it.

More info at Apache Tomcat 8 Configuration Reference.

Additional information 

• Apache Module mod_proxy
• Apache Module mod_proxy_ajp
• Apache Module mod_rewrite
• mod_rewrite, a beginner’s guide
• Using Apache Virtual Hosts and ProxyPass Together
• Rewrite HTTP To HTTPS
• Redirect to SSL
• Configuración SSL de Tomcat
• How To Create an SSL Certificate on Apache for CentOS 6