OpenSSH, the client that comes with most Unix/Linux systems, provides the capability for proxying through one ssh server to another. This is a completely client side configuration.
- Setup your Secure Passwordless Login for ssh.
- Open your ssh config for editing. ie. vim ~/.ssh/config
- Add a host entry for the servers you want to access through the ssh proxy.
Host *.domain !gateway0?
ProxyCommand ssh gateway01.domain exec nc %h %p
Now you should be able to login to internal servers transparently from your workstation. This will hold true for interactive ssh, sftp, and scp.