System-Wide Transparent FTP Tunneling with Fallback

In this example, transparent FTP tunneling is configured to secure file transfers to three different subnets (10.70.20.0/24, 172.16.8.0/21, and 192.168.93.0/25). Configuration is done system-wide affecting all FTP batch jobs and interactive sessions to those three subnets. FTP connections to other addresses are not affected.

In this example, Tectia SOCKS Proxy is configured to fall back to plain FTP if securing the connection fails. Fallback is a usable feature during the migration phase but must be turned off once all connections are working correctly.

Do the following steps:

Copy the /opt/tectia/etc/ssh-socks-proxy-config-example.xml configuration file to /opt/tectia/etc/ssh-socks-proxy-config.xml (if it does not exist yet).

Edit the file to enable fallback to plaintext FTP for transparent FTP tunneling:

  <filter-engine>
     <rule ip-address=".*"
           ports="21"
           action="ftp-tunnel"
           profile-id="id1"
           username-from-app="YES"
           hostname-from-app="YES"
           fallback-to-plain="YES" />
  </filter-engine>

Start the SOCKS Proxy if it is not already running.
If the SOCKS Proxy is already running, take the updated configuration in use as instructed in Reloading ssh-socks-proxy configuration.
Edit the system-wide FTP configuration file SYS1.TCPPARMS(FTPDATA) to include the following lines:
```
SOCKSCONFIGFILE  EXAMPLE.SYSTEM.SOCKS.CONF
FWFRIENDLY       TRUE
```

Create a new SOCKS configuration data set EXAMPLE.SYSTEM.SOCKS.CONF with the following contents:

sockd @=127.0.0.1 10.70.20.0 255.255.255.0 
sockd @=127.0.0.1 172.16.8.0 255.255.248.0 
sockd @=127.0.0.1 192.168.93.0 255.255.255.128 
direct 0.0.0.0 0.0.0.0