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Researched:

I have been reading up on reverse FTP; the concept of how it works as well as the configuration. However none could fully fufil my understanding base my the scenario I was give. Most of the web sites only states the commands to forward any FTP request to a proxy server. What I wanted to learn exactly how each individual nodes in the setup has to be configured (except the firewall)


Scenario:

[Internal FTP Server] -> [DMZ Reverse FTP Server] -> [External Clients Computers/Servers]

When a legitimate client computer/server on the external network make a FTP request to the FTP server in the internal network, there will be a reverse FTP server which forwards the request between them.

There will be two firewalls in between the reverse FTP server, external client and internal. A typical back-to-back firewall topology.

FTP server will be installed on the internal FTP server (Normal Mode)

  • The internal FTP server has to be configure to forward and receive any FTP request to/from the reverse FTP server in the DMZ
  • The reverse FTP server has to be configure as a proxy server that can receive and forward any FTP request
  • External clients/servers should only be able to see the public IP address of the interface of the public facing firewall
  • Both servers, the FTP server and the reverse FTP server are running on Linux RHEL 6 OS


What at the commands and steps should I take to perform such configurations on the FTP server as well as the reverse FTP server? Is there any security measures that I should take note of?

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This can be done using SUSE's "proxy-suite", which is actually just a program (ftp-proxy). It's old (its last release is from 2005), but works quite well. The FTP clients from Internet would connect to this proxy, which would be in the DMZ, and the proxy would connect to the server in the internal network.

There is no native rpm for RHEL, but you can modify the src.rpm (it has some SUSE-specific package names and quirks) to build one.

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