zen.org Communal Weblog

March 10, 2005

AIM/MSN/Yahoo inside a firewall

Filed under: — brendan @ 15:16 IST

Say you want to talk to your wife or remote co-worker on AIM, but you’re on a system inside a firewall. All is not lost if the firewall is really picky about what ports it’ll allow you to use—and you have no ability to change the firewall’s settings. If the SSH port (22) is open on the firewall, you’ve got a workaround as long as you can SSH to a remote host that’s able to be configured for you or by you.

In the description of what I came up with (derived from the suggestions of others via google), both the home system and laptop I describe are running version 9.2 of the SuSE Linux distribution. In theory, however, this should work with any client using a recent copy of OpenSSH. Please feel free to correct me if this isn’t true. 🙂

Originally, I suggested that you need to install dante and dante-server on the remote server you’ll be using to do the work of the connection. However, it turns out OpenSSH has the DynamicForward option which does the work for you, making the OpenSSH server and client use the SOCKS5 protocol to handle the connection. Many thanks to Justin Mason for pointing it out.

On the laptop that’s roaming from place to place, install just the GAIM instant messaging package. (In theory, if we had to use dante-server then you’d also install the dante client on the laptop so KDE can use the SOCKS for its own IM client kopete. However, we’re using GAIM because I’ve been unable to make KDE+kopete work for me in this. And since OpenSSH is doing the work, we don’t need to install the extra package on the laptop.)

From inside the firewall, log into the remote system with the command “ssh home“. The ~/.ssh/config file (or wherever your SSH client keeps its configuration) should have

   Host home
     HostName 1.2.3.4  # server external IP address
     # If we were using dante and dante-server, we'd need:
     #LocalForward 1080 127.0.0.1:1080
     # However, we can just use this:
     DynamicForward 1080

On the laptop, run GAIM and go into Preferences, selecting Network. Under ProxyServer choose Proxy type SOCKS5, and set Host to 127.0.0.1 and Port to 1080. Click on Close.

To connect, click “Sign On” in the GAIM window. (You’ll need to make sure that each account in GAIM has “Auto-login” selected so more than just AIM are used.)

In theory, the SSH tunnel letting you use SOCKS should now make any/all of your AIM, MSN, and YahooMessenger IDs be online successfully. I’ll be interested to hear of any problems others might have trying to get this to work.

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