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I work at a university but I often work remotely. There is a cluster computer at the university that I need to be able to interact with, but its behind a firewall. Let's call the firewall F and the cluster C.

In the past, in similar situations, I would just ssh to F and then ssh from F to C. This works fine, and I can connect doing so. The problem is, unlike other firewalls I've dealt with in the past, F does not have anything installed besides ssh. I need to be able to get files to and from C, and I can't do so through F without scp.

My university offers an sslvpn for this situation, but for reasons that I and the technical staff cannot figure out why I cannot ssh into local computers when on the sslvpn. For example, although from an external network I can ssh into F and then to C, I cannot ssh into F OR C (or any other computer on the network) when connected to the sslvpn. The connection just times out.

I've thought that ssh tunneling might be the solution - tunnel my traffic through F to C (as I understand it). Then I can scp to C or from C and the packets will just be tunneled through F. However, I'm having trouble setting this up, and no guides I've found online have been helpful. I want to be able to have an interactive shell on C which is tunneled through F.

I've tried:

~  ᐅ ssh -f -R 3000:me@firewall_here:5222 me@cluster_here -N
~  ᐅ ssh -f -L 3000:me@firewall_here:5222 me@cluster_here -N

I've also tried following this guide: http://www.revsys.com/writings/quicktips/ssh-tunnel.html and this guide:

With either of those commands, the connection times out when trying to connect to m3@cluster_here just as if I was on the sslvpn. I have no idea how to fix this. Any help appreciated - and can run any commands for more useful information.

  • You're missing a 2nd URL in the paragraph after the example ssh commands. Also what is this sslvpn? Is it the name of the actual product the university uses or something else? – slm Dec 2 '14 at 12:45
  • See this tutorial on how to proxy SSH connections through a bastion host (DMZ): backdrift.org/transparent-proxy-with-ssh. Also there's sshuttle and this thread from SU: superuser.com/questions/62303/… – slm Dec 2 '14 at 13:30
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Not exactly the answer you asked for, but you should be able to transfer files through an SSH connection:

sending

ssh user1@firewall "ssh user2@cluster \"cat > remote_file\" "  < local_file

fetching

ssh user1@firewall "ssh user2@cluster \"cat remote_file\" "  > local_file

EDIT:

There are also terminal based file transfer tools like "zmodem"

  • Here's the output when I try this: Permission denied, please try again. Permission denied, please try again. Permission denied (publickey,gssapi-with-mic,password). – The Wind-Up Bird Dec 11 '14 at 13:33
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Read about Reverse SSH. Maybe this will help you. I use it to connect to remote storages behind NAT.

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