Bug 2393 (Rem.dyn.port.Fwding)

Created attachment 2615 [details]
Remote dynamic port forwarding patch against OpenSSH Portable 70860b6d07

It would be nice to have the fourth combination of static/dynamic and local/remote TCP port forwarding. Local static (-L), remote static (-R) and local dynamic (-D) combinations are already supported. What is missing is the remote dynamic port forwarding.

Remote dynamic port forwarding would be useful to extend possibilities and deployability of both remote static port forwarding and local dynamic port forwarding.

Remote static port forwarding allows client to reach a particular TCP port on their client machine from a remote SSH session. With remote dynamic port forwarding clients would be able to execute arbitrary programs on a remote SSH server completely retaining their TCP connectivity and network identity. If their TCP payload doesn't support SOCKS protocol natively, it can be packed into SOCKS requests with a SOCKS wrapper such as proxychains or socksify. Similarly, using remote static port forwarding clients can publish a single service on the SSH server. With remote dynamic port forwarding they would be able to publish their whole connectivity to all users of the SSH server or even to all those, who have access to a particular TCP port on the server.

Local dynamic port forwarding enables clients to use basically any SSH server as a SOCKS proxy server. However, sometimes it's not possible to operate an SSH server on a particular machine (due to firewall constrains, impossibility to bind sockets to privileged ports, etc.). Remote dynamic port forwarding allows the potential proxy servers to circumvent the condition of running an SSH server with running just an SSH client. Local dynamic port forwarding allows clients to assume the connectivity and network identity of the SSH server. Remote dynamic port forwarding in combination with local static port forwarding allows clients to assume also the connectivity and network identity of fellow SSH clients.

There is already a patch against OpenSSH portable (commit 70860b6d07461906730632f9758ff1b7c98c695a) that provides remote dynamic port forwarding support.

http://d3s.mff.cuni.cz/~steinhauser/openssh.html