user based SSH reverse proxy

TL;DR Simple setup instructions

To setup the user-based reverse proxy the following steps should be performed.

On the Gateway

1. Create a key-pair for password-less login on the ssh-server using ssh-keygen
2. setup syncronization of authorized_keys for the proxied users
   • If the syncronization should be done via scp, add the public key of the ssh-server to the gateways' authorized_keys. It is recommended to call the syncronized variant authorized_keys2
3. Install sshproxy_gateway
4. setup ~/ssh/proxy/gateway.conf, a sample file is shipped
5. symlink the name of the ssh-application to sshproxy_gateway

On the ssh app-server

1. If syncronization should be done via scp, create a key-pair using ssh-keygen
2. Install sshproxy_host
3. add command="/usr/bin/sshproxy_host",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty ssh-rsa ... to the (not syncronized!) authorized_keys file
4. maybe setup path of authorized_keys in your application. the name authorized_keys2 is recommended for that file

Problem discussion

The complete discussion of the problem can be seen in the Wiki