zomo tech

OpenSSH’s SOCKS forwarding

Sunday, 18. 01. 2009  –  Category: stash, web

It’s always great to discover a feature in a tool you use everyday. Someone pointed out to me that, in addition to local and remote port forwarding, OpenSSH also offers what it calls dynamic application-level port forwarding. Put more simply, OpenSSH can act as a local SOCKS proxy punting the traffic out the remote end of the connection:

ssh -Dlocalhost:1080 -C host.example.com

You can now aim your browser’s SOCKS settting at localhost:1080. Bonus points for using a locally-hosted PAC file to determine which traffic is routed via the proxy:

function FindProxyForURL(url, host) {
  if (shExpMatch(host, "*.example.com"))
    return "SOCKS 127.0.0.1:1080"
  else
    return "DIRECT";
}

For getting sight of servers behind a firewall without remote proxies (hello Privoxy) and continual browser fiddling this is ideal. Thanks Murb!