Run Acrolinx Behind a Reverse Proxy

We recommend setting up a dedicated reverse proxy for your Acrolinx Core Platform as a standard security measure. This reverse proxy should be on the same computer as the Core Platform.

A reverse proxy not only ensures that any traffic to your Core Platform is secure, it will also help you avoid other security issues. For example, on Linux a reverse proxy will help you avoid privilege escalations – you can create a dedicated Acrolinx Core Platform user with restricted permissions, and let the reverse proxy listen on ports that require superuser permissions. The Core Platform uses the default ports 80 and 443, which require superuser permissions.

In this article, you'll learn how to set up a reverse proxy for Acrolinx. We use NGINX at Acrolinx, so we've included an NGINX configuration example to show you how we do it. You can use our example as a template – especially if you're on Standard Stack it should work as is. You can of course use other reverse proxy software if you prefer.

Configuring Your Reverse Proxy

To run your Core Platform behind a reverse proxy, you'll need the following configuration:

  • Your proxy server is secured with an SSL certificate. Acrolinx doesn’t support self-signed certificates.
  • Your proxy server has Transport Layer Security (TLS) termination enabled.
  • Your proxy server adds forwarding information. The following headers are supported:
    • Forwarded as defined by rfc7239

    • X-Forwarded-Host and X-Forwarded-Proto

  • The proxy timeout limit is set to at least 360 seconds.

Example Configuration with NGINX

Below you can see an example configuration for an NGINX reverse proxy. This is the configuration that we use at Acrolinx, and we know it works for Standard Stack installations. If you have a different setup, you can still use this example as a template, but you should adapt it to your specific environment and needs. For the full details on how to set up a reverse proxy with NGINX, take a look at NGINX's own documentation on reverse proxy configuration and TLS termination.

A Tip for SELinux

By default, Red Hat Enterprise Linux runs Security-Enhanced Linux (SELinux) in "Enforcing" mode. This will block NGINX from connecting to Acrolinx's port (8031), unless you allow it.

To allow Acrolinx's port in SELinux, follow these steps:

  1. Open a command line as root.
  2. Run getenforce. This checks the mode that SELinux is running in.
    If it returns "Disabled" or "Permissive", you don't have to do anything.
    If it returns "Enforcing", continue to the next step.
  3. Run semanage port -l | egrep '(^http_port_t|8031)'. This lists the ports that NGINX is currently allowed to connect to.

    Example output:
    http_port_t                    tcp      80, 81, 443, 488, 8008, 8009, 8443, 9000

    If you don't see port 8031 in the output, continue to the next step.

  4. Run semanage port -a -t http_port_t -p tcp 8031. This adds port 8031 to the security context.
  5. To make sure port 8031 was added successfully, run semanage port -l | egrep '(^http_port_t|8031)' again.

    Example output:
    http_port_t                    tcp      8031, 80, 81, 443, 488, 8008, 8009, 8443, 9000
  6. Restart NGINX.
Example NGINX Configuration
server {
    listen       80 default_server;
    listen       [::]:80 default_server;
    server_name  _;
    return       301 https://$host$request_uri;
}
server {
    listen                      443 default_server ssl;
    listen                      [::]:443 default_server ssl;
    server_name                 _;

    ssl_certificate             /etc/ssl/certs/cert.crt; # Your SSL cert goes here
    ssl_certificate_key         /etc/ssl/private/cert.key; # Your SSL key goes here

    ssl_session_timeout         5m;
    ssl_protocols               TLSv1.2; # Add TLSv1.1 here if required for older versions of Java
    ssl_prefer_server_ciphers   On;
    ssl_ciphers                 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';

    location / {
        client_max_body_size        0;
        proxy_set_header            X-Real-IP $remote_addr;
        proxy_set_header            X-Forwarded-For $remote_addr;
        proxy_set_header            X-Forwarded-Proto $scheme;
        proxy_set_header            Host $host;
        proxy_pass                  http://127.0.0.1:8031;
        proxy_read_timeout          900s;
    }
}

Integration-Specific Extra Steps

If you're using any of the following integrations, there are some extra steps: